lEF 

ICAL 
APHY 



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Separate Geography for Each Grade 

BY FRANCIS T. MILLER AND JOHN W. UAVIS 

4A GEOGRAPHY 

{New York City — The Earth) 



4B GEOGRAPHY 

{The Earth — The Continents) 



BY HARMON B. NIVER 

5A GEOGRAPHY 

{North America — United States) 



6B GEOGRAPHY 

{United States) 



EY HARMON B. NIVER AND EDWARD D. FAKRELi, 

GA GEOGRAPHY 

{Canada, Nezvfoundland, Mexico 
West Indies, Central America, South America) 



6B GEOGRAPHY 

{Europe) 



7A GEOGRAPHY 

{North America, United States, and Its 
Dependencies 



7B GEOGRAPHY 

{Asia, Africa, Australia, Oceania) 

BY JOHN W. DAVIS AND THOMAS H. HUGHES 

8A GEOGRAPHY 

{Mathematical and Physical) 

HINDS, NOBLE & ELDRP:DGE 
30 Irving Place New York City 



OCEAN 




^PANAMA-CANAL 

moM VN 
AEROPLANl 




How Man Changes his Exviroxment 



A BRIEF 

PHYSICAL 
GEOGRAPHY 



BY 
JOHN W. DAVIS 

DISTRICT SUPERINTENDENT OF SCHOOLS 
NEW YORK CITY 

AND }M^ 

THOMAS H. HUGHES 

EVANDER CHILDS HIGH SCHOOL 
NEW YORK CITY 



HINDS, NOBLE & ELDREDGE. Publishers 
30 Irving Place New York City 



Copyriglit, 1914, by Hinds, Xoblc & Eldredge 



SB 



PREFACE 



'3^-=V 



The authors hope that this book will be welcomed in those schools 
in which the time is lacking to master the bulky books on Phj^sical 
Geography, while yet the desire exists to devote to the subject some- 
what more of endeavor than is required by the few pages on this 
subject found in the average school-geography. 

Geography is considered to-day as a description of the earth only 
in so far as that will account for the earth as the home of man and hi^ 
occupations. It seems as if we can no longer justify a purelj^ physi- 
cal geography; now we want to know how man lives and why he lives 
in this or that way. The most important fact about the earth is that 
it is a human planet: men not only live upon it but also make a liv- 
ing out of it. Man changes the earth, and the earth changes man. 
It is a far cry from the nebulous mass that was thrown off from the 
sun ages ago, to a contemplated aeroplane flight across the Atlantic 
or the completion of the Panama canal; but these are the limits of 
geographical study, and we have to bear in mind always that man is 
himself a part of nature. In the usual division of the study into 
physical, commercial, and political branches, the relation of the 
human species to its natural environment, which is the keystone of 
all geographical science, is generally lost. 

In this volume, reference has been made, wherever possible, to the 
human side of natural phenomena, to their help or hindrance to man 
in his progress. The treatment of many points has been kept sugges- 
tive rather than exhaustive, since, in the tracing of causal relations, 
the geography of this grade lends itself so readily to the development 
of the reasoning powers of pupils. Among these relations are, for ex- 
ample, altitude and temperature, weather and habits of daily life, 
mountain trend and rainfall, heat belts, winds and rain, topography 
and drainage, climate and vegetation, and the dependence of man on 
his physical environment. The physical features of the earth may 
also be used to develop or interpret human industries, mode of life, 
dress, and other human characteristics. t y 

2 ' / ^>€^ 

©CU388626 

DEC -I 1914 ^^ 



PREFACE 3 

Various features of the earth and the solar system, which affect 
the life of man only indirectly, have been treated in this book. Mis- 
conceptions of the most simple facts about the earth's crust are al- 
ways with us. And though the only " practical " reason for studying 
the moon, for example, is the effect of this planet on the earth's tides, 
yet there are many simple astronomical facts that it may rightly 
be considered "a disgrace and a misfortune not to know." 

The illustrations are intended to serve as the basis for class discus- 
sions and questioning, and it is hoped that they will be studied and 
interpreted with the text. The questions and exercises are designed 
to promote thought. The unit map idea has been employed, and par- 
ticular attention has been given to the rigid exclusion of irrelevant 
matter from the maps. All rational work in general geography must 
be founded on physiography: the fact that the pupil is al)out to enter 
upon a general geographical review in the 8B Grade has been kept in 
mind in the preparation of the closing chapters. 



To the courtesy of owners of copyrighted pictures we are indebted 
for permission to reprint in this book, as follows: Underwood & 
Underwood, pictures on pages 104, 127, 156. Swiss Federal Rail- 
roads, pictures on pages 83, 35, 39, 45, lOG, 107, 108, 203, 210, and 
217. The Century Magazine, picture on page 211. G. P. Putnam's 
Sons, pictures on pages 13, 15, 77. The New York Times, map on 
page 73. 



CONTENTS 

CHAPTER PAGE 

I. The Sun and the Solar System 7 

II. The Earth as a Planet 18 

III. The Crust of the Earth 25 

IV. The Motions of the Earth and their Effects .... 48 
V. Latitude; Longitude; Time 58 

VI. The Moon; Its Revolutions and Phases 75 

Vll. The Earth's Atmosphere; Dew, Fog and Cloud .... 84 

VIII. Volcanoes and Earthquakes; Glaciers 97 

IX. The Great Wind Systems 112 

X. The Rainfall of the Earth 121 

XI. The Causes and Effects of Ocean Movements .... 131 

XII. The Weather of the World 145 

XIII. Climate and its Causes 159 

XIV. The Effects of Climate on Plants 171 

XV. The Effects op Climate on Animals 181 

XVI. The Effects of Climate on Man and his Activities . . . 193 

XVII. How Man Conquers his Environment 208 

Index 222 

Appendix i 

MAPS AND CHARTS 

The Panama Canal Frontispiece 

Western Hemisphere 4 

Eastern Hemisphere 5 

PoHtical Map of the United States 60-61 

PoUtical Map of the World 64-65 

Map of Volcanoes and Earthquake Regions 102 

The Principal Wind Belts of the World . . . . ' 115 

The Rainfall of the World 123 

Mean Annual Rainfall of the United States 129 

The Principal Ocean Currents 140 

United States Weather Map 148 

United States Weather Map 150 

A United States Storm Chart 151 

The Light Zones and Heat Belts 158 

Isothermal Map of the United States for July 160 

Isothermal Map of the United States for January 162 

Isothermal Map of the World in January 166 

Isothermal Map of the World in July 168 

Population Map of the World 201 



GEOGRAPHY 



CHAPTER I 



THE SUN AND THE SOLAR SYSTEM 



The Stars. — Very few of us, if asked to tell the number of desks 
in our schoolroom or the number of aisles separating them, could do 
so without counting them; and yet we have been looking at these 
things every day since 
the beginning of the 
term. Neither could 
we tell the number of 
steps in the stoops of 
our houses up which we 
have run so many times. 
In the same way, we 
have neglected to ob- 
serve carefully many of 
the great works of Na- 
ture that deserve our 
attention. For exam- 
ple, few of us have 
given very much atten- 
tion to those twinkling 
lights in the skies that 
we call the stars. 

A very wise writer 

once said that if these F^°- l- The Pole star with the Big and the Little Dipper. 

stars should appear only 

one night in a thousand years, every one would gaze up with wonder 
and would remember the sight forever. But, just because they do shine 
so patiently for us night after night, we persistently neglect them. 
Many of us, perhaps, have never imagined that some of these twink- 

7 




8 



THE SUN AND THE SOLAR SYSTEM 



lings in that great space we call the sky may be other worlds greater 
than ours, making their own never-ending journeys. 

Fixed Stars and Wanderers. — In order to learn a little more 
about them, it would be well for us to select a star on the next clear 
night and to get it on a line made with our eyes and the corner of the 
roof of any building that is between us and the star. We can mark 
with chalk the exact spot on which we stand when we get the star in 
line. Then make a similar observation for several other bright stars. 
When we return to these spots, several hours later, or the next night, 
and chalk-mark our position in line with the same stars, we shall see 
that our stars are no longer on the same straight line as before. The 
stars will appear to have moved slowly across the sky, most of them 
keeping together. But since the position of each one is fixed, in rela- 
tion to the others, they are called fixed stars. 

We can easily find the star group called the Big Dipper as shown 
in Figures 1 and 2. The stars marked "pointers" are so called because 
they seem to point to the Pole star which is always above the north 

pole of our earth. The Big Dipper 
moves with the other stars and once 
every twenty-four hours it revolves 
around the Pole star. The Pole star 
is stationary in the sky, and the 
group called the Little Dipper also 
moves around it. 

There are some stars, however, 
that do not twinkle and that move 
from night to night at a different 
speed from that of the fixed stars w*e 
have been observing. They do not 
keep the same position in relation to 
the others but make great mysterious 
wanderings through space, always 
coming back, however, to the same 
position in which we first saw them. 
These stars are called planets (wan- 
FiG. 2. Notice the pointers and the derers) ; our earth is one, and even 

earth s axis, each in hne with the Fole i • , 

star. the sun is one, because every morn- 




THE sun's FAMJLY OR THE SOLAR SYSTEM 



ing during the year each appears among a different group of fixed 
stars. 

The Sun's Family or the Solar System. — Witli tiio aid of 
great telescopes, astronomers have found that there are eight hirge 
planets revolving around our sun, and about five hundred smaller 
bodies, all making up a family that the sun supports with light and 
heat. Figure 5 shows us that these move at different distances 
from the sun, along the paths called orbits. The planets have no 
light of their own, and little, if any, heat. Indeed, if they had, 

we should not be able to live 
on the earth. But we see 
them shining at night by 




reason of the sun's light re- 
flected from their surface, as 
a mirror reflects the light of 
a lamp. All the members of 
the solar family resemble one 
another. They are spherical 
in form, and each one rotates 
on an axis of its own while 
revolving about the sun. 
The great difference between 
them is in their respective 
sizes and in the periods of Fig. 3. Tho small i.i.turr sh,.\v.s the nipiMr as 
time requiretl for their revo- T'" t*»''"^!«'\ ^'''; X''""''''. ^t''^'lT'- .Tv-, "^''^^''/^ 

' ^ the vicnv ohtaiiicd throuKii the Mount « ilson tele- 

lution. We must always bear scope (Fiu. l), which i.s .sixty iiulios in diameter. 



10 



THE SUN AND THE SOLAR SYSTEM 



in mind that from another planet in the sun's family our own earth 
would appear only as a dull star. 

Names of the Planets. — Our earth is the fourth planet in size 




Fig. 5. The planets and their orbits in the solar system. 

and the third in distance from the sun, requiring 365j days to complete 
its revolution. Nearer the sun is Mercury, named after the messenger 
of the Greek gods, completing its revolution in a year of 88 days. Be- 
tween the earth and Mercury is Venus, the most brilliant of the planets, 
named after the goddess of beauty. Then in order come Mars, Jupi- 
ter, Saturn, Uranus, and Neptune, all of which have been likewise 
named after the Roman gods. Neptune and Uranus are so far away 



THE SUN AS THE SOURCE OF HEAT AND LIGHT 



11 



from us that they cannot be seen without the aid of a telescope. All 
the others are easily observed, Venus, for example, appearing either 
as the Evening Star or the Morning Star, and Mars being recognized 
by its reddish tinge. 

The nearer a planet is to the sun, the more rapid is its or])ital move- 
ment and the shorter its year. For example, Venus, being a little 
nearer to the sun than the earth, completes its year in 225 daj^s. (See 
Appendix 1.) Jupiter requires twelve of our years to travel once 
around the sun. Some of these planets are more distant from us than 
we are from the sun. Uranus, for example, is so far away from us 
that if an express train had started out from it 2,000 years ago to 
travel to our planet, even though it traveled sixty miles an hour, it 
would have completed to-day only a little more than one half its 
journey. 

The Sun as the Source of Heat and Light. — Wo know that 
the sun, the central and largest member of the solar system, is a mighty 
power-house from which 
come all the forces that 
set in motion the earth and 
its life. We shall see that 
it is the sun's heat which 
causes the winds to blow, 
the clouds to ascend, the 
rivers to flow, the forests 
to grow, and man himself 
to live. We are familiar 
with the effects of over-exposing the skin to its rays, and we have seen 
how a lens can produce fire by concentrating upon one spot the ra\'s 
spread over a circular space. And yet, just as this page now receives 
but a small part of all the light given out by an electric bulb, so the 
earth being so small a sphere in the sun's family gets but a tiny part 
(2,000,000,000) of the entire amount of energy given off by the sun. Let 
us imagine a great sheet of ice, ninety-eight feet thick, covering all the 
earth. If the quantity of heat received by the earth in a j^ear were 
uniformly distributed, it would be sufficient to change this mass of ice 
to water in one year. 

To attempt to measure the light of the sun by any of the means 




Fig. 6. The earth's tiny share of the sun's heat. 



12 THE SUN AND THE SOLAR SYSTEM 

at our disposal is a hopeless task. The light of countless millions of 
wax candles could not begin to give us an idea of the povv^er of this 
wonderful star of day which, 92,750,000 miles away, sends us so small 
a fraction of its beams, yet accomplishes results so marvelous. 

The Surface of the Sun. — We are never able to see the sur- 
face of the sun because great masses of burning gas surround it, very 
much like the burning vapor enveloping a sponge when we soak it in 
alcohol and ignite it. These fiery gases blaze up to incredible heights 
above its surface; for example, if the earth were ablaze as is the sun, 
the flames would soar high enough to reach our moon. The surface of 
the sun seems to be in violent commotion as if it were in constant 
eruption. Moreover, through great telescopes, we are able to observe 
peculiar patches on its surface. These spots are called sun-spots, which 
travel across its face and disappear on the opposite side. This move- 
ment takes place because the sun also rotates on its axis. We do not 
know just what these spots are, but we are sometimes able to trace 
their influence upon climatic conditions on our earth. 

REVIEW QUESTIONS. — (1) Can you think of any use sailors might make of 
the Pole star? (2) Mention some ways in which the planets resemble one another. 
(3) Explain the difference between a fixed star and a planet. (4) What difference would 
there be in the appearance of the earth to an observer on Mercury and one on Jupiter? 
(5) What is the approximate number of days in each of our seasons? (6) Assuming 
that their axes are inclined at the same angle as that of our earth, give the approximate 
number of days in each of the seasons on Mercury, Mars, and Neptune. (See Appen- 
dix ii.) (7) Can you think of any other instrument than the lens which makes use of the 
sun's heat? Try to find out what a solar engine is and how it is used. 

EXERCISES. — (1) Locate the Big Dipper in the sky and sketch it in your note- 
book. (2) Standing on the same spot at the same hour, draw this star group on three 
successive nights. Account for the differences in the diagrams. (3) Watch the appearance 
of the moon for six successive nights and report in class what you observed. (4) Cut 
from cardboard circular pieces to illustrate the relative sizes of the planets. (5) Since 
light travels 186,000 miles per second, how many minutes will it take for light leaving the 
sun to reach the earth? (6) Make a diagram of a lens concentrating the sun's rays at 
one spot. (7) Tell how the amount of heat we receive from the sun changes in the four 
seasons. Give all the results of these changes that you can think of. (8) Suppose the 
distance of the earth from the sun were 46,000,000 miles. What changes can you think of 
as taking place on the earth? (9) Suppose the earth were changed in position with Ura- 
nus, what differences might be expected? (10) Make a list of the planets in order of size; 
a list in order of distance from the sun. 

The Origin of the Solar System. — Where did the earth come 
from? What is the moon we see at night? How do Mars and Jupiter 



THE ORIGIN OF THE SOLAR SYSTEM 



13 



come to be journeying forever around the sun? Why is the planet 
Venus round? What force keeps Uranus at a distance of 1,800 million 
miles from the sun, permitting it neither to retreat another million 
miles nor to advance a thousand miles nearer? Why is that great 
abyss that contains the Pacific ocean on the earth? Where did the 
water come from that fills it? 

Most of us have observed that when an automobile spins rapidly 
over a muddy street, the tires repeatedly cast off particles of mud. 
Thes? particles fly off in the same direction as the wheel is traveling, 
and when we try to brush them from our coats, we observe that they 
are generally circular in form. 

It is believed that millions of years ago all these bodies that we know 
as the sun's family existed not as separate units but as one great cloud 
or nebula 
filling all 
the space 
within the 
great orbit 
of Neptune. 
This enor- 
mous cloud 
of highly 
heated va- 

fi Fig. 7. The planet Jupiter. Fig. 8. The ringed planet Saturn. 

por, alter a 

long period of time began to cool and to grow smaller in expanse. As it 
did this, it took on a rotary or spinning motion like that of a top, bulg- 
ing out at the equator and flattening at the poles. Then, just as our 
automobile tire did, this great cloud began to throw off from its middle 
part, or equator, masses of fiery vapor in the form of rings. These ring 
masses of heavy cloud gradually took on a spherical shape and acquired 
their direction also from the whirling movement of the pariMit mass. 
Invisible lines of force permitted them to travel only a certain distance 
away from the central mass and then forced them to swing around 
in their orbits forever at that distance. 

In this way, we suppose the eight great planets flaming with heat 
were thrown off from the sun and have ever since been revolving around 
it. Immediately these great rings of vapor themselves began to cool 




14 



THE SUN AND THE SOLAR SYSTEM 



and contract, while keeping up their whirhng motion. Then, just 
as the sun did, many of them threw off smaller rings. The best type 
of these smaller bodies is our own moon, which we believe was cast 
off from the earth. Astronomers find that the size or volume of the 
moon is about the same as that of the great gash in the earth's sur- 
face that we call the bed of the Pacific ocean, and they suggest that 
perhaps the moon-mass originally filled that depression. 

Figure 7 shows that the great planet Jupiter is still so hot that 
its atmosphere is filled with clouds of steam, while Figure 8 indi- 
cates that Saturn is in the process of throwing off rings of vapor which 
may become moons to circle about the parent bod}'. 

We all know, despite the care with 
which a cook smooths over the covering 
of an apple pie before she puts it into 
an oven to bake, that this crust, in 
the process of cooling and recovering 
from the abnormal swelling produced 
by the oven's heat, ■^"ill crack and 
wrinkle and pit. The crust has become 
too large for the pie and must lie in folds 
or wrinkles to fit the plate. In just the 
same way the great planets, after mil- 
lions of years, began to cool on the outer 
Fig. 9. The effect on an apple of parts; and this crust, shrinking after 
ea mg an coo ng. ^j^^ terrific heat, produced all the irreg- 

ularities that on the earth we know as continents, sea-bottoms, moun- 
tains, and valleys. You know that when steam from the spout of a 
kettle strikes a cold window-pane the vapor becomes liquid, which 
you see on the glass. In a similar way, as the space about these cool- 
ing planets grew colder, the steam surrounding them also cooled and 
became liquid, at one time covering all the surface of such planet; 
then, as the irregularities in the crust were formed, the water flowed 
into the deep places and produced the oceans. 

Satellites, Comets, and Meteors. — Most of the stars that 
we see at night are not members of our solar sj^stem but are fiery- 
bodies like our sun, with their own sj^stems of planets. They are so 
far away that they appear only as twinkling lights. We can realize 




COMETS 



15 



the wonderful size of the universe when we refiect that some of these 
great suns arc so distant that the rays of their light which are now 
reaching our eyes, must have started over two thousand years ago 
on their journey to the earth. 

There arc other members of our solar system wliich are not plan- 
ets, but the results or outcome of the rings of vapor cast off by the 
planets. These are called moons or satellites (" guardians "). They 
shine by light reflected from the sun and revolve about their parent 
planets in the same direction as do the respective planets around 
the sun. Mercury and Venus are the only planets whose satellites 
are not to be seen. Figure 5 shows the moons of the other planets. 

Comets are fiery bodies which revolve about the sun in very elon- 
gated orbits and some of them come near enough to the earth to be visi- 
ble to us. 
The mass or 
''head" of 
these mj'ste- 
rious travel- 
ers is al- 
ways very 
small, but, 
in the form 
of vapor in 
the sky, the 
size appears 
enormous. 

o- fUri ^'^- ^f*- ^^^ comet of 1861 retreating from the sun. Fic. 11. Hal- 

k5ince iney loy's comet approaching the sun. 
travel with 

great speed, this cloud-like mass trails out into a " tail " behind 
them, often thousands of miles in length. The tail follows the head 
when they approach the sun but streams out in front of the head as 
they retreat from the sun. In 1759 Edmund Hallc}', an English 
astronomer, predicted the appearance of a comet because he had 
traced out its orbit around the sun. This traveler, now called Hal- 
ley's comet, comes inside our solar system and circles around the sun 
once every seventy-five years. It made its last appearance, as shown 
in Figure 11, in 1910 and will be due again in 1985. 




16 



THE SUN AND THE SOLAR SYSTEM 



Meteors. — Everybody has at some time beheld the strange 
sight known as falUng stars or shooting stars or meteors. On any 
clear night a few of these can be seen darting across the sky. They are 
supposed to be very small, solid bodies, perhaps but a fraction of an 
ounce in weight, which plunge through our atmosphere with such 
speed that they are set afire and consumed by the heat of friction, 
developed when they strike our atmosphere. Other meteoric bodies 
of larger mass, called meteorites, are not entirely consumed and often 

fall upon our earth. These 
are found to be of stone or 
iron, the largest fragment 
ever seen to fall weighing 
about a quarter of a ton. 
We know very little about 
the origin of these bodies. 
Some people suggest that 
they have been shot out of 
the sun or that the}^ were 
cast into space b}^ vol- 
canoes on the surface of 
the moon. 
Earth the Home of Man. — In this wonderful way was the 
earth created b}' a Divine ^Master who waited millions of years for it 
to shape and prepare itself before he placed upon it his greatest cre- 
ation, Man. It is our work now to learn more facts about our own 
planet as it revolves in space, to learn what other conditions Man 
has to meet on it, and then to see how he succeeds in making it a 
better home by mastering one after another the forces of nature in 
action upon it, how he changes the land, makes use of the waters, 
and attempts the conquest of the air. 




Am. Mus. Xat. Hist. 



Fig. 12. The Cape York meteorite which weighs 
36.5 tons. 



REVIEW QUESTIONS. — (1) What is the importance of the sun in the solar 
system? (2) Make a sketch of a wagon-wheel revohdng s-n-iftly in a muddy road. "VMiat 
does this illustrate about the formation of the solar system? (3) If some of the fixed stars 
are great suns like our own, how is it they appear so small? (4) Wliat is the difi'erence 
between a satellite and a planet? (5) Tell the difference between a comet and a meteor. 

(6) A scientist has declared that if Halley's comet were compressed, it could be contained 
in a tea cup. What does this indicate about the substance of which a comet is composed? 

(7) What might be the result if a comet struck our earth? (S) How is it that we do not 



EXERCISES 17 

Bcc the moon clearly in the day time? (9) How would the appearance of the sun change 
to a person who might be imagined approaching it on a comet? 

EXERCISES. — (1) "Write in a paragraph an explanation of the way in which we 
suppose the planets were formed. (2) Secure a smooth apple and place it in a hot oven 
until it is baked. Bring it to class and explain the appearance of its skin. ■\\'hat does 
this illustrate about the earth? (3) Describe the appearance of the earth as it would be 
if the vapor around it had never been cooled into moisture. (4) Make sketches showing 
the appearance of a coniot approaching the sun and retreating from it. (5) Make a draw- 
ing showing Mars, Venus, and the earth in their orbits. 



CHAPTER II 



THE EARTH AS A PLANET 



The Earth in Space. — In learning how the earth is fitted to 
be the home of man, we have seen that it is a great sphere supposed 
to have been cast off from the sun milhons of years ago. It is now 
whiriing through space at the rate of a thousand miles a minute, 
or more than one and one half million miles per day, in a never- 
ending journey around the sun. This movement is called the planet's 
revolution. 

The Size and Shape of the Earth. — As a result of its rapid 
turning when a molten mass, it began to flatten at the north and south 




Fig. 13. The land and the water hemispheres. 

poles so that now it is hardly a perfect sphere but resembles an orange 
in shape. Such a body is called an oblate spheroid; and a line con- 
necting the two poles is about twenty-six miles shorter than a diam- 
eter through the earth at the equator. A polar diameter is about 
eight thousand miles in length and our planet is nearly twenty-five 
thousand miles in circumference. It would take an express train, 

18 



THE SPHEKES OR LAYERS OF THE EARTH 



19 



moving a mile a minute, seventeen days and nights of continuous 
travel to complete the journey around it. 

We can sec from Figure 13 that the water which formed when 
the earth was cooling now occupies seven tenths of its surface, the 
remainder being occupied by the continents and islands. The larger 
part of the land area is in the northern hemisphere which includes 
almost all the large continents. The southern hemisphere is practi- 
cally a water hemisphere. The center of the land hemisphere is near 
the cit}^ of London while the opposite end of an axis driven through 
the earth at this point is the center of the water hemisphere. This 
point is near New Zealand. 

The Spheres or Layers of the Earth. — We know very little 
about the central body or core of the earth. We believe that it is 
still a glowing hot mass of nickel-iron under great pressure. This 
ball is called the Centersphere of the earth. Pressing in on this por- 
tion is the crust of the planet, some twenty miles in thickness, that 
we call the Rocksphere. Where this crust is irregular and depressed 
the great Hydrosphere, or watersphere, 
fills the cavities. We believe that, ages 
ago, this water envelope covered the 
whole earth, until the great gaps we call 
the ocean beds were formed and then 
the water ran into them. As the crust 
sank in some places, when the center- 
sphere cooled and contracted, it was dis- 
torted into folds and wrinkles. It is 
these great upfolds that form the con- 
tinents, lifting themselves above the hy- 
drosphere of the planet. On these con- 
tinents the crust was forced into narrower folds forming mountain 
ranges and> during the rising of these, the rocksphere was often broken 
and folded. Through the cracks in the crust, formed in this way, 
molten rock sometimes came forth in great quantities such as to build 
the peaks and cones we call volcanoes. The crust of the earth is still 
changing; and the rising of the land has often been accompanied 
by earthquake shocks caused by the breaking and slipping of the 
layers of material in the rocksphere, as they moved one upon the 



ATMOSPHERE 



■r!T&RSH-r-<i 



Fig. 14. A section of part of the earth. 



20 



THE EARTH AS A PLANET 




Fig. 15. 
elevations. 



other. Finally, enclosing both land and water in a great sea of air, 
at the bottom of which we move about, is the earth's Atmosphere. 

This belt of air ex- 
tends about forty 
miles from the planet 
in all directions but 
the greater part of 
the air is near the 
earth's surface. 

Proofs of the 

Earth's Shape. — 

'JjromAs!:^ ^ gy crawling over 

The broadening horizon seen from different a circular lamp shade 

can see but very 
little of its surface at any one moment, and that very little must ap- 
pear flat to the insect. In much the same way our earth, really 
spherical, appears flat to us looking along its surface, so that we can 
easily under- 
stand to-day 
the fear of 
the ancients 
in venturing 
out of sight 
of land. 

We all know 
that when we 
look out from 
the windows 
of the first 
story of our 
school build- 
ing we can see 
more of the 
street than 
we can from 

the ground; and if we mount to the roof we can see the roofs of 
many houses below us and the surfaces of many streets. If we 




Fig. 16. Steamer entering port. 



POLES, AXIS, EQUATOR 



21 




Fig. 17. A view of a distant 
ship as seen through a telescope. 



could go farther up in an aeroplane, we might see the whole net- 
work of streets that make up our city. However, our range of vision 
would always be bounded by the curved 
line, where earth and sky seem to meet, 
that is called the horizon. 

This horizon seems both to enlarge and 
to sink as we ascend above the surface; 
whereas, if the earth were a flat surface, 
our field of vision would not change, no 
matter how high we mounted. The horizon 
is always circular, which would not be the 
case if the earth's form were not very 
nearly spherical. 

Suppose you were in positions A and B 
in Figure 15. How would your observations prove the shape of the 
earth? A ship leaving port drops over the horizon line and disap- 
pears from our view because of the earth's spherical curvature. How 
do the steamers in Figure 16 prove this? Figure 17 shows a view of 

a steamer obtained through the 
glasses of a marine telescope. Ex- 
plain why the vessel should have 
this appearance. 

Hold an orange in front of a 
lamp and observe its shadow on a 
piece of paper. Sometimes the 
earth has the position of that orange 
when the planet is between the sun 
and the moon. How can the ap- 
pearance of its shadow (Figure 18) 
be used as a proof of the shape of 
our planet? 

Poles ; Axis ; Equator. — We 
know that this planet turns or rotates on its axis once in twenty-four 
hours, and that it moves through space revolving around the sun in a 
fixed orbit once in every year of 365^ days. At the ends of the earth's 
axis are the poles, the north pole lieing the one above which the Pole 
star, far out beyond us in space, seems to twinkle. (See Figure 2.) 




Fig. 18. The circular shadow of the 
earth thrown on the moon. 



22 



THE EARTH AS A PLANET 



NORTH POLE 




As the earth turns, its axis does not keep a position straight up 
and down but it is inehned to the plane of the orbit in which it moves 
as shown in Figure 20. This angle of inclination from the perpen- 
dicular is 23^ degrees. So that as 
the earth moves about the sun, the 
north pole first leans awaj^ from the 
sun. When the planet has reached 
the other side of the sun, the north 
pole leans toward the sun. 

We know the equator to be an 
imaginary line half way between the 
poles, di^ading the sphere into the 
northern and southern hemispheres. 
All the places along the equator have 
a faster rotary motion than any other 
part of the world — a thousand miles 
an hour. They correspond really to 
the points around the rim of a wagon-wheel which swing around 
rapidly when the wheel is in motion while all parts of the spokes 
toward the hub move at a slower rate, till at the hub of the wheel 
the motion is very slight. What then is the extent of the rotary 
movement at the poles of the earth? 

Gravity and Gravitation. — When you drop a lead pencil it is 
drawn not to the right nor to the left nor does it move upward to the 
ceiling, but it falls as far as it can toward the center of the earth. 
When a leaf falls in Siam, opposite us on the globe, it too is drawn 
to the center. Should the engine of an aeroplane miles above the 
surface be shut off, the machine glides always down to the earth, and 
not off to Venus. There is a force coming from the center of our 
planet which attracts every atom of matter to it and holds it in place. 
This force is gravity. Without it we would be swept from the earth 
when it rotates at such terrific speed, the waters of the sea would be 
dashed from its surface, and your lead pencil would flj' up instead 
of being drawn down! 

How can it be, moreover, that the earth revolving at the speed 
of one thousand miles a minute does not fly off from its orbit and 
away into space? Why does our faithful satellite, the moon, attend 



REVIEW QUESTIONS 



23 




Fk;. 20. Notioo how tho axis is incliiiorl tfjwarrl a linn that is 
pcrpendicuhir to the plane of the orbit. 



upon the earth so steadily and never dash off to another planet? What 
power holds Mars and Uranus whirling round and round the sun? 
To demonstrate this force we can place several blocks of wood, large 
and small, in a bathtub over night and observe their position the 
following morning. 

In studying the solar system we said that invisi])le lines of force 
held the planets in their orbits just as a string holds in its orbit a 
stone you whirl 
about your body. 
This force, the 
attraction be- 
tween two large 
bodies, we call 
gravitation. The 
onward sweep of 
the planets is 
really the result 

of two forces. The first is the centrifugal force which causes a planet 
to keep moving in a straight lino and drives it away from the sun. 
The second force is gravitation which tends to draw the planet back 
to the sun and away from a straight line. As a result, the orl)it of 
a planet becomes nearly circular around the sun, and the body keeps 
up its revolution forever. 

Gravitation differs from gravity because the latter is only the 
attraction of the earth for all bodies on it. The greater the differ- 
ence in size between the bodies the greater is the force of gravita- 
tion. Hence the sun, over a million times larger than the earth, has 
little difficulty in controlling its motion. The same force holds the 
moon in its or])it around the earth. 

REVIEW QUESTIONS. — (1) How far does the earth travel in its orbit in one 
hour? (2) Into what sphere of the earth docs a volcano open when it is in eruption? 
(3) What proportion of the earth's diameter is crust? (4) If you were on a ship entering 
a harbor, would you see the base or the roofs of the high liuildings first? ^Vhy? (5) Is 
the fact that Magellan sailed around the earth a proof that it is round? (6) Give three 
other proofs of the earth's shape. (7) Which diameter of the earth is longer, the cquato- 
ri;il or the polar? (8) Explain the difference between gravity and gravitation. (9) How 
high above the earth can an aeroplane rise? Why? (10) If an aeroplane should ascend 
vertically to a distance of two miles and then descend, would it return to the same 
point it left? (11) What differences might be observed if the earth lost its force pf gravity? 



24 THE EARTH AS A PLANET 

(12) Show how our words up, down, and level depend on gra\'ity for their meaning. 

(13) State some changes that might result in the western hemisphere if the ocean level 
were one thousand feet higher. Refer to Figures 21 and 22. (14) What changes might 
result if the ocean level fell one thousand feet. 

EXERCISES. — (1) Make diagrams of a circle and an oblate spheroid. Compare the 
lengths of their axes. (2) Thrust a knitting needle through the stem end of an orange to 
the other side. By means of this show the two movements of the earth. (3) Write a par- 
agraph giving an account of the way in which water came to be on the earth. (4) Draw two 
circles to scale and show the relative amount of land and water on the earth. (5) Take the 
orange in (2) and tilt it to show the inclination of the earth's axis. Now move it around 
a lamp. What do you observe about the position of the north pole? About the south pole's 
position? (6) Make a drawing to show the part of a steamer you would see first if you 
were on a high building in lower New York. (7) Draw the surface of the ocean as you 
would see it from this position. (8) Draw a circle to represent the earth. Place a dot for 
New York and draw a line to represent all the places in the northern hemisphere which 
rotate around the axis with the same speed as that city. (9) Make diagrams like 
Figure 20 showing what the earth's position would be if the angles of inclination of the 
axis were 33J°; 45°; 90°; 0°. 



CHAPTER III 
THE CRUST OF THE EARTH 

The Restless Surface. — We have seen that as the coohng 
earth shrinks, its crust wrinkles, rising in some parts and setthng in 
others. This has left its crust far from regular. In some places 
mountains rise 5| miles above the sea level, in others sea valleys 
drop down 5| miles. The Japan islands, the Philippines, and the 
West Indies are merely the tops of mountain ranges rising from 
great ocean depths. Peaks in the Andes are over 40,000 feet above 
the ocean floor at points just off the coast. The work of changing 
the face of the planet is never complete. The earth's surface is 
never at rest. It is always undergoing changes. Movements of the 
crust are constantly elevating or lowering the land, so that sea-bot- 
toms have been raised to make continents, mountains have been 
formed, and lands have been lowered beneath the sea. Other forces 
are tearing away the surface, smoothing down the high places, and 
trying to fill up the great gaps. The weather crumbles rocks, and 
rivers carry the waste off to the sea, glaciers rip and tear the land 
while the forces of the ocean eat it away. This leveling down of the 
crust is called erosion. This great struggle between the earth's crust 
to raise the land and the other forces to level it goes on forever; as 
a result of it we have all the irregularities of the surface which man 
must struggle with and conquer one after another to make his home 
on this planet. 

The Great Continents. — The real margin of the continents is 
beneath sea level, so that they are really uplifted blocks of crust 
generally surrounded by the waters which once covered them. The 
land extends off shore for several miles forming what are called 
continental shelves. Islands rising above these shelves like Great 
Britain are called continental islands to contrast them with oceanic 
islands that lie like those in the Pacific far from any land. 

25 



THE CRUST OF THE EARTH 








^^^ '"^^i 



Fig. 21. Relief map of North America. 




THE CRUST OF THE EARTH 



27 




^"'.5^- 



FiQ. 22. Relief map of South America. 



28 



THE CRUST OF THE EARTH 




Fig. 23. Relief map of Africa. 



Continents consist of great backbones and ribs of mountain sj^s- 
tems connected by plains and plateaus built of rock fragments worn 
from the mountains. These are cut by rivers which form valleys 
and drain the land. 

I . North America. — IMountain ranges give to the continents 
their outlines; for example, the Western highland, the Appalachian 
system, and an old range which ran westward from Labrador have 



SOUTH AMERICA AND AFRICA 



29 



given to North America its triangular form. Waste torn from those 
mountains in past ages formed the great plains and plateaus. All 
the irregularities around the gulf of Mexico are due to mountain 
ranges continuing along the continental shelf, while the irregular coast 












"^^52!^ 



Fig. 24. Relief map of Australia and the East Indies. 



/ 



> 



line is due to the sinking of the land which permitted the sea to enter 
valleys. New York harbor, Long Island sound, Hudson baj^, gulf of 
St. Lawrence, and all the peninsulas and islands were thus formed. 
2. South America and Africa. — Observe how the mountains 
of these continents have determined their triangular forms. Since 
there has been no extensive sinking of the land except in the south- 
ern part, the South American outline is very regular. ]\Iountain 
uplifts near the coast have made Africa mainly a l)road plateau. The 
sinking has been very slight, hence there are few harbors. 



30 



THE CRUST OF THE EARTH 




^^ 




J 









'■/ 



J,?'^ 



.X 



_lMllmlBMllllli 



-:^ 







^ 










ANTARCTICA 



31 



3. Australia. — Observe how the mountain chains failed to 
give this huge island a triangular form. Tasmania and York perv- 
insula are merely continuations of the continental shelf, wliile the 
irregular coast line is due to the sinldng of the continent. 



I .^RICA:^■r- 




OCEAN 



PA C/F/C 
OCFAN 



TASMANIA wm* ' ia , 



NEW/CALAND 




Am. Muj. Nat. Hist. 



Fig. 26. A view of Antarctica. 



4. Eurasia. — Europe and Asia are really one continent, an 
irregular triangle in form, extending from Spain to Bering strait, 
and then down to Borneo. Its great peninsulas from Kamchatka 
around to Scandinavia are all due to the presence of mountains. Its 
great islands are the raised portion of the continental shelf. Its 
splendid commercial coast line is due to the sinking of the land which 
produced the Baltic, the North, and the Irish seas. 

5. Antarctica. — This newly discovered continent apparently 
consists of a central plateau with sloping coastal plains. At one part 
a mountain range, with peaks 15,000 feet high, extends toward South 
America. Its size is about that of North America and its shape is 



32 



THE CRUST OF THE EARTH 



also triangular. An ice sheet of enormous thickness renders this con- 
tinent unavailable for the purposes of man. 

The Rocks of the Crust. — Almost everj^where on the land 
of these continents there is a layer of loose rock fragments, the sur- 




Am. ilo^. Nat. Hist, 



Fig. 27. The top of the world. 



face part of wliich is called soil; but wherever this soil coating is 
penetrated to a depth great enough, solid rock is found in great layers 
or strata. Mountains have no soil covering because the decayed rock 
falls away before the soil can accumulate. These strata of the rock- 
sphere are of many useful varieties, such as granite, sandstone, or 
limestone. In addition, the rocks contain laj^ers of coal, beds of salt, 
and all the minerals of which man makes use. 

Some rocks are very hard and others are soft; so that as the land 
is worn down by water, valleys are formed where the soft rocks 
give way, while hills and ridges stand out where the rocks have more 
resistance. 

Weathering and Erosion. — The crumbling away of rocks is 



WEATHERING AND EROSION 



33 



called weathering. It is produced by the action of water, frost, and 
air, and through the efforts of plants and animals. Water dissolves 




Fig. 28. Rook strata wliich have been tilted during the growth of mountains. Nf)ticc 
the work of erosion. 



some of the minerals in rock and causes it to fall apart. In cold 
climates, moisture, penetrating the rocks, freezes in winter. When 
it freezes, it must expand, and in this way layers of rocks are often 
broken off by frost action. Air, warm in the day and cold at night, 
causes rocks to fall away by expanding them; again, the roots of 




Fig. 29. The backbone of a couliiniit. 



34 



THE CRUST OF THE EARTH 



plants often manage to split them. Earthworms, woodchucks, and 

other burrowing animals stir up the soil and permit water to enter 

rock more easily. This action 
of weathering results in the 
formation of soil from decayed 
rock; it causes landslides and 
avalanches on mountains; it 
makes valleys broader; and 
it roughens the appearance 
of rocks. In addition to 
the work of these agents of 
weathering, erosion, or the 
leveling of the land, is carried 
on by winds along the coasts 
and in deserts; by rivers, 
which carry off the waste 
caused by weathering; by the 
ocean, whose waves, tides, and 
currents attack the coast line; 
and by glaciers, which trans- 
port rock fragments for long 
distances. The force of grav- 
ity is also active here in 
drawing all the particles as 
far down to the earth's center 
as possible. By these forces, 
the continents would have 
been leveled dowTi to the sea 

long ago, were it not for the movements of the crust which constantly 

lift plains, plateaus, and mountains still higher. 




Fig. .30. A stream helping in the work of erosion. 



QUESTIONS. — (1) How do mountains determine or affect the shape of continents? 
(2) What difference would follow in the form of North America and of South America if 
the ranges extended east and west? (.3) Locate five continental and five oceanic islands. 
(4) What is the effect of the coast line on man's acti^aties in a continent? Illustrate 
from Africa and North America. (5) Account for the irregular coast line of northern 
Europe; the scarcity of good harbors in South America; the British Isles; New York 
harbor; the eastern coast line of Asia. (6) Why are there so many irregularities in north- 
eastern North America? (7) Explain the presence of southern California, Cuba, and 



THE WORK OF RIVERS 



35 



Porto Rico; Madagascar; Tasmania; Kamchatka; East Indies. (8) What is erosion? 
What is weathering? Name the forces which produce their effects. (9) What evidences 
have you seen at the seashore of the changes going on over the earth's surface? On a 
country road? In the mountains? In a city? (10) Toll about the effects of frost on the 
Palisades along the Hudson river. 



The Work of Rivers. — Rivers aid in changing the surface of 
the land by carrying off the materials, or detritus, supplied by weath- 
ering and rain. The 
amount of sediment 
that they carry 
varies widely. Some 
rivers are clear, 
some are heavy and 
muddy. The detri- 
tus also varies from 
large boulders to 
gravel, sand, and 
clay. Every river 
carries some sedi- 
ment, though it may 
be invisible. In ad- 
dition to acting as 
carriers, rivers at 
some time in their 
history are busily at 
work cutting their 
channels. They not 
only cut their beds, 
but also eat away 
their banks and thus 
produce wide val- 
leys. A stream rush- 
ing down a steep 
slope with great vol- 
ume over soft rock will cut a deeper channel than a river which meets 
hard rock or one which is poorly fed with water. A river with little 
sediment, like the Niagara, cannot cut a valley as well as one with 




Fig. 31. A river cutting a gorge deeper. 



36 



THE CRUST OF THE EARTH 



a heavy load of detritus like the Colorado, which has cut an enor- 
mous canyon. 

The basin of a great river is made up of all the land sloping to- 
ward it whose water and detritus reach the ocean through its efforts. 




Fig. 32. A river during a dry period unable to carry off its load of detritus. 

Minor streams which combine to feed the great river are called its 
tributaries and compose with it a river system. The elevated ridges 
running above continents which determine whether the rainfall of a 
slope is to feed into one river system or into another, are called 
divides. These separate river basins. 

Young River Valleys. — A river's life work, then, is to wear 
away a great belt of land. When it begins this work, it is called a 
young river; and the valley it produces, narrow in proportion to its 
depth, is called a young valley. All gorges, ravines, glens, and can- 
yons are young valleys. Men rarely settle in young valleys, because 
there are no gentle slopes adapted to agricultural purposes. 

Sometimes a broad valley contracts for a short distance to a nar- 
row chasm, because of a barrier of hard rock or a mountain ridge 
not 3^et worn away by the river. These short, young valleys are 



YOUNG RIVER VALLEYS 



37 




Fig. 33. Notice how the harder rock has resiated the agents of erosion. 




l'"i»;. 34. A rixcr in a niahuc \allc.\'. N'ote tlic oM, worn-down innnntains. 



38 



THE CRUST OF THE EARTH 



called water gaps, and are of importance because all roads and canals 
in the valley' must pass through them. 

A young river, again, following an irregular course in the moun- 
tains produces rapids, waterfalls, and cascades. Sometimes it runs 
into a barrier and cannot pass. Then it forms a lake or pond and 
flows steadily until it raises its level high enough to find an outlet. 
The force of waterfalls is of great value to man in suppljdng power 
to mills, dynamos, and other machines; while lakes are much used 
as lines of travel and commerce. When large lakes have been drained 




Fig. 35. The Labrador peneplain. 



or have dried up, the bottom forms a very fertile plain because it 
has for years received the fine sediment from the waters. The great 
wheat fields in the northern part of the Great Central plain are in 
the basin of an enormous lake long since dried up. 

Mature Valleys. — As a river cuts wider and wider into its 
valley, carrjdng off soil now from one side, now from the other, and 
as weathering acts on the soil and rock, a young valley becomes 
mature. These valleys slope gently, bear fertile soil, and become 
thickly populated. Highways and railroads are run through and 
great farms are cultivated. The Connecticut river drains a broad, 
mature valley of this kind. The river's work is done when it has cut 
down to sea level; it becomes feebler and instead of carrjang its 



OLD RIVERS AND VALLEYS 



39 




Fig. 36. A Swiss valley dug out by a great glacier. 



detritus to the ocean, it now deposits this in its own valley. The 
flat plains it builds are called alluvial plains, and, if flooded at times 
of high water, as in the Nile valley, flood plains. They are good 
farming regions on account of their fine soil, lev(>l surface, and near- 
ness to water. 

Old Rivers and Valleys. — A river and valley become old 
when the slopes have been reduced through weathering and erosion 



40 



THE CRUST OF THE EARTH 




Fig. 37. The delta of the Mississippi. 



until the region becomes very flat with just enough inchne to make 
the river run. An old land surface, reduced to a low, rolling surface 
is called a peneplain (almost plain). Old rivers always build alluvial 

plains in their lower portions, 
like our Mississippi, and the 
Ganges in India, because they 
have not enough current to 
carry out the large amount of 
detritus brought down by their 
tributaries. 

Deltas and Drowned Val- 
leys. — When a river empties 
into the ocean or any body of 
quiet water, its current is sud- 
denly checked, and it drops 
the detritus it carries. This builds up in the form of the Greek 
letter A (delta). Sometimes, as in the case of the Mississippi, 
the Nile, and the Orinoco, the main stream divides at the head 
of the delta and flows across it in 
several branches. The delta soil 
makes excellent farm land. A large 
percentage of the human race is now 
living on deltas and alluvial plains, es- 
pecially in China, Holland, and India. 
Where the land is settling, in- 
stead of rivers building deltas out 
in the ocean, the salt water flows 
into the river basins so as to sub- 
merge the valleys or drown them. 
Where this happens to an old or 
mature valley, broad irregular arm& of 
the sea, called estuaries, are formed. 
San Francisco bay, the Hudson river, 
Delaware bay are estuaries which 
are of great commercial importance. 
When this happens to a young valley, it is narrow and deep, and we 
have steep walled fiords, as in Norway, Alaska, and Southern Chile. 



1 




1% *' 




SAN FRAMCI^m^ 


^: 


: M, 




n m',^P||m. 




— i^'^'^^il 


^k 


-n '» '^^^^fc ' 


Jk; 


O %^ 


^fe^^:S 







Fig. 3S. Estuaries formed by the 
drowning of vallej^s. 



PLAINS 



41 



QUESTIONS. — (1) Describe the work of a river from youth to old age. (2) De- 
fine river basin, flood plain, tributary, and detritus. (3) How does a young valley differ 
from a mature valley? Explain the effects upon it of winds, water, and weathering. In 
which valley arc men most likolj' to settle? Why? (4) IIow was the Delaware water gap 
formed? Why should river, wagon roads, and railroads pass through it? (5) What vari- 
ous uses does man make of rivers? (6) IIow is a lake formed liy a ri\'er? What uses are 
made of lakes in North America? In Europe? (7) What is a divide? From the physical 
maps, tell where you would expect to find divides on the continents. Make a list of the 
great river systems on the continents. (8) What use does man make of deltas? Locate 
five great deltas. (9) How are estuaries and fiords formed? What is their importance? 




Fii;. •"iD. A Norwegian fiord formed by the drowning of a valley. 



Plains. — As the earth's crust raises the land, the lovol conti- 
nental shelves are lifted from the water to form sloping coastal 
plains. The plain extending from New Jersey to Mexico along the 
North America coast was built in this way. These plains are gen- 
erally sandy and poorly adapted to agriculture except in the higher 
tracts. Interior plains are sometimes formed, as in Eurasia, of 
detritus washed into a sea-bottom which has been destroyed by the 
lifting of the crust. 

Tundras, found in Siberia and Greenland, are barren plains in 
winter, and in summer, thawing only at the surface, vast swamps. 
Steppes are open, grass-covered plains generally too arid for fann- 
ing. The Great Plains of North America were originally a sea-l)ot- 
tom also. Here few elevations rise above the prevailing level of the 



42 



THE CRUST OF THE EARTH 



country, the slopes are gentle, and they are either arid and treeless 
or moist and adapted to agriculture. Prairies are large areas of plain, 
treeless when discovered, a condition due to the fires set by Indians 




Fig. 40. The broad coastal plain of New .lorsoy. 

in buffalo hunts, or to the fact that the soil favored prairie grass 
more than tree-growth. Plains similar to these described above are 
found in each of the continents under various names. 




Fig. 41. A view of the Siberian tundra. 



Plateaus. — When the earth's crust is raised up in mountains, 
the plains of the country on either side are also raised so that they 
become plateaus or elevated plains. Along the base of the Appa- 



DESERTS 



43 



lachians, the plateau is 2,000 feet above the sea; north of the Hima- 
layas the plateau height is 10,000 feet. Plateaus, like rivers and 
plains, have life histories. Young rivers cut them into rugged forms 
with divides, and produce deep valleys with falls and rapids. As 
they mature, the valleys 
grow broader through 
weathering and erosion, 
the surface lowers, and 
finally in old age the 
land is level again. 

A canyon is the 
deep, steep-sided valley 
of a 3'oung plateau 
river. The Colorado 
river flows in one for 
200 miles, and though 
it has cut down 6,000 
feet, the stream is still 
young. Of course, a 
river may have been 
working for 8,000 or 
even 80,000 years and 
yet have a young val- 
ley. A river's life work 
cannot be measured by 
years but only by the 
form of its valley or 
canyon. 

Plateaus are often 




Fig. 42. The Colorado canyon. 



cold and arid, and some are true deserts, though in moist countries 
they are forest-covered. They are usually sparsely settled, and cattle- 
raising on arid plateaus is the leading occupation, while lumbering is 
followed on some moist plateaus. In some cases plateaus have been 
entirely worn away and only a few flat-topped table mountains 
remain, with vertical sides. These are called mesas (tables) and 
buttes. 

Deserts. — These are regions in which few forms of life can find 



44 



THE CRUST OF THE EARTH 



an existence. Antarctica by reason of its ice and cold is a desert. 
The name desert, however, is usually applied to those regions where 
the rainfall is so scanty that only especially adapted animals and 
plants can live in them. Some rain falls in the driest of deserts even 
though, as in Peru, dry periods of seven years may be known. Most 
deserts are plains and plateaus with much sand, though in Utah and 
in the Sahara mountain ranges are found. Winds move the sand 
about in severe sand storms, and form belts of sand dunes which 
have been known to cover cities. Except on the oases, which are 
either scattered springs or else places where streams descend from 
mountains which are high enough to get moisture, deserts are un- 
favorable to settlement by man. 

The Life History of a Moiintain. — We have seen how, as the 
heated interior of the earth cools and shrinks, the crust settles down. 

Since it is now too large to fit the 
centersphere, it wrinkles and the 
layers of rock bend upward to form 
a mountain sj'-stem. As the layers 
or strata slowly bend, the strain 
becomes too great and the rock- 
sphere splits and one part slips upon 
another, or they support each other 
in a great ridge. This jars the earth, producing earthquake shocks; 
while through the deep fissures thus formed, lava may rise forming 
volcanic cones. 

As soon as the land rises, the agents of weathering and erosion, 
winds, air, rain and rivers, heat and cold, plants and animals, attack 
it; and the higher the mountain rises, the fiercer they become in 
their efforts to wear it down. Valleys are formed between the ridges, 
streams Cut gorges across them, the hard rock remains as ridges and 
peaks, while the soft rocks are cut away, forming valleys and passes. 
IMountains in this stage, like the Alps, the Andes, the Rockies, and 
the Himalayas are called young mountains. The folding of the 
strata and the later erosion of the land are of great importance 
to man, for through these means the valuable mineral deposits 
of mountains are brought to light and mining is made possible 
[Figure 44). 




Fig. 43. Strata broken bj^ great pressure. 



THE CLIMATE OF MOUNTAINS 



45 



Finally the uplifting of the rocksphere ceases, but the forces are 
still busy broadening the valleys and lowering the peaks. The 
mountains become smooth, forested, and sloping, and, like the Appa- 
lachians and the mountains 
of Norway and Scotland, 
are now called mature. In 
the end, after countless cen- 
turies, they become old and 
are reduced to a series of 
rolling hills or even level 
surfaces. New York City 
and Philadelphia are situated on such old worn-down mountains. 
Sometimes, however, another uplift will come and give new life to an 
old mountain region. When this happens, its life history is repeated. 



W^ 


^m 


'>« ■>^-C>?S?^^i=^- ^ -- ^=^. 



Fig. 44. Strata bent upward and brol- 
the layer of coal. 



Note 




Fig. 45. Notice the timlicr lino and the snow lin 



The Climate of Mountains. — The liiglier a mountain rises, tlic 
colder it l)econies. Some have perpetual snow on their sunnnits, and 
glaciers in their valleys. The line marking this belt of snow is called 



46 



THE CRUST OF THE EARTH 



the snow line, and the Hne above which trees cannot survive is 
called the timber line. Day and night bring great changes in tem- 
perature, and we have learned how frost action splits off laj^ers of 
rock. The strong winds, the heavy rains, blow or wash these frag- 
ments down; and the melting snows above the timber line, where 

there is no vegeta- 
tion to hold the soil 
and rock together, 
form streams to 
carry the detritus 
away. 

Owing to the 
climate and soil 
conditions, moun- 
tains are sparsely 
settled. Agricul- 
ture may flourish 
at the base, but the 
area available for 
cultivation be- 
comes smaller the 
higher one goes. 
Grain fields are found higher up, and grazing areas that support 
herds for a month or so in summer are common above the timber 
line. Above this, however, plant and animal life is very sparse. 

Relations of Mountains to Man. — IMountains have always 
been barriers, hemming in people and animals in one region and 
checking their passage by ruggedness and coldness. The Appala- 
chians, Alps, Pyrenees, and Himalayas have all been effective bar- 
riers and boundaries, conquered by man only with difficulty. The 
important parts of a mountain system, then, are the lowest points 
in the ranges where man can cross most easily. 

On the other hand, mountains afford beautiful scenery and are 
inspiring. They are summer resorts for health and pleasure, and 
are important as timber reserves; while many ranges are Nature's 
great storehouses of gold, silver, lead, copper, iron, coal, and build- 
ing stones. 



SHMHIk^ j^^SiI^ 


'"^^ 


^ 


^^^ 


A^^ " Y '■■''^►•^ SL ' ■''ip*^ ■ " 




'^-^A 


i 


V'^ f '^^"^ 




'"^i^ -. 


V- 












mr:\ 


■■^. -.,-- -?^ 


'wmmw 


W mm.. : 




4^ 





Fig. 46. A young mountain range in the Canadian Rockies. 



QUESTIONS 47 

QUESTIONS. — (1) Explain the work of the crust in mountain building. (2) Tell 
the life history of a mountain. (3) Make a list of the great mountain ranges on the con- 
tinents. (4) From the physical maps, tell where you would expect to find the great 
plains of the world. The great plateaus. (5) Explain the difference between coastal and 
interior plains. (G) Describe possible effects of avalanches and landslides. (7) What 
forces are active in attacking mountains? (8) Explain why man should be interested in 
prairies, oases, peneplains, canyons, steppes, mesas, and tundras. ('.)) AVhat do snow 
lines and timber lines indicate to man? (10) Explain the effects of mountains on com- 
munication and commerce in Europe, Asia, and South America. On the history of nations 
in these continents. (11) Tell about their effects on the characteristics of mountaineers 
in the Alps, in Scotland, Kentucky, and the Pyrenees. 



CHAPTER IV 



THE MOTIONS OF THE EARTH AND THEIR EFFECTS 



Rotation. — The rotation of the earth occasions what we call 
sunrise and sunset. For many years people believed that the sun 
moved across the heavens every day and that the earth was station- 
ary. We can understand their error when we recall that as we ride 
in a rapidly moving car trees, fences, and houses often appear to be 
moving in a direction opposite to that in which we are traveling. It 

seems as though we are stationary. 
In just this way, the rotation of the 
earth causes the sun and the stars 
to appear to move, to rise and to set, 
while in reality we are riding by 
them. Since the sun rises for us in 
the east, it is plain that the earth 
is turning eastward: that is, from 
west to east. One complete rota- 
tion is made in about every twenty- 
four hours; and since the earth is an 
opaque sphere, only one half of its surface can be lighted at one time. 
The boundary line between the light and dark parts forms a great 
circle called the Circle of Illumination. 

Effects of Rotation. — The spinning motion of the earth on its 
axis leads to the following results: (1) The movement produces the 
alternation of day and night. (2) It leads to the knowledge of the 
earth's axis, equator, and poles. (3) It produces the flattening at 
the poles. (4) It causes the apparent movement of the skies in the 
opposite direction. 

Revolution. — While the planet spins once around on its axis 
in one day, 8664 of those daily rotations take place while the earth 

48 





r^ —. 


s\\ ' — 


— S 


\ y\ t — 


ti 


"^ \ A 


n 


/ 


< — 


s 


^^^ 








< — 


R 




a 


I 1/1 * 


y 






— 5 






^ — 






Fig. 47. The circle of illumination pass- 
ing around the earth. 



REVOLUTION 



49 



is making its year-long journey about the sun. In doing tliis, it 
travels through an enormous orbit of 585,000,000 miles, so that 
every month we are able to view different constellations or groups 
of stars. We have already learned that the axis of the earth is not 
straight up and down like a lead pencil held perpendicular to your 




Fig. 48. Position of the earth in its orbit each month. 

desk but is inclined 23|° from the perpendicular to the plane of the 
earth's orbit, as in Figure 50. The end of the axis, the north pole, 
remains in one position pointing always to the Polo star. 

In Figure 4S we can see the earth circling about the sun at the 
different months in the year. Notice the movement of the north 
pole from Scptc^mbcr 23 away from the sun until Decemb(>r 21, and 
then its gradual return toward the sun until the position of March 



50 



THE MOTIONS OF THE EARTH AND THEIR EFFECTS 




Fig. 49. The position of the earth at the 
equinoxes. 



21 is reached. Now it swings toward the sun until the position of 
June 21, and then away, until September 23 is reached once more 
and the year is ended. In this long trip, the axis has always remained 
parallel to its first position. 

Day and Night over the Earth : Equinoxes : Circles. — In 
Figure 49, which shows the earth on ]\Iarch 21, although the axis is 

inclined, neither pole is turned 
from the sun. The circle of 
illumination, therefore, extends 
from pole to pole. At the equa- 
tor the sun's rays are vertical, 
and day and night each lasts for 
twelve hours all over the earth, 
since it will turn completely in 
twentj'-four hours. This time 
is called the spring or vernal 
equinox (equal days and nights). 
Next, in Figure SO the earth has moved to the position of June 
21. The sun's rays, since the axis is tilted toward them 23|° from 
the perpendicular, reach the same number of degrees beyond the 
north pole and give us the location of one of the great circles of the 
earth — the Arctic circle. While the earth was in the position of 
March 21, the sun's rays were 
vertical at the equator, but 
during April, IMay, and June 
they have crept northward on 
the earth and are now vertical 
at a point 23|° north of the 
equator. This gives us the 
location of the tropic of Can- 
cer, which is on the line on 
which the sun seems to turn. 
During this period from 
March 21 to June 21, day is continuing week after week, at the 
north pole. The Eskimos have their long stretch of unbroken day- 
light. The midnight sun in the Arctic circle appears also at midday, 
and circles around the heavens near the horizon. It reaches its 




Fig. 50. The position of the earth at the 
summer solstice. 



THE SOLSTICES 



51 



highest point on June 21. At the south pole, just the opposite 
conditions prevail, the area about the pole being shrouded in weeks 
of darkness. 

At that part of the earth's surface near the equator, the sun re- 
appears every morning; by noon it mounts directly overhead, and 
then seems to set. At this region, the days and nights are always 
of equal length (twelve hours); at all other places they are un- 
equal, except when the earth is at the equinoxes in March and in 
September. 

On September 23 we find the pole has swung away from the sun, 
the rays are again vertical at the equator, days and nights are equal 
over the earth. Here we have the autumnal equinox. 

Figure 51 shows us the earth three months later when the pole 
has swung farther away from the sun. We get the location of the 
Antarctic circle, 23|° beyond the south pole, by the extent of the 
sun's rays. The tropic of Capricorn is located 23|° below the equa- 
tor because the sun's rays are then vertical on that great circle. The 
word tropic means " turning-point," since the sun, when at either 
of the two tropics, seems to turn and start back — either northward 
or southward, as the case may be. The south pole, at this time, is 
enjoying unbroken day and knows no night, while the Arctic regions 
are in darkness; and we in the northern hemisphere are having 
shortest day and longest night. \2Ji°\ 

The Solstices. — At Decem- 
ber 21, the sun in our northern 
hemisphere is at its lowest posi- 
tion in the heavens, and short 
days, long nights, and winter 
prevail. Since the sun seems 
to stop at this low point for a 
few days before it begins to rise, 
we call its position the winter 
solstice, or " standing-still " of 
the sun. On June 21, it reaches its highest point in the sky for us 
and begins to return to the autumnal equinox. June 21 then is called 
the summer solstice, the sun appears north of the equator, and long 
days and sunnner prevail in the northern hemisphere. 




Fig. 51. The position of the earth at the 
winter solstice. 



52 



THE MOTIONS OF THE EARTH AND THEIR EFFECTS 




Fig. 52. The midnight sun at North Cape, Norway. 



Variation in the Length of Day and Night. — We can see 
that the change in length of day and night is due to the incHnation 
of the earth's axis to the plane of its orbit. From Figure 50 notice 
that when the sun is north of the equator, more than half of the 
tropic of Cancer and therefore of every line parallel to it, in the 
northern hemisphere except the equator, is in the sunlight at a time. 

At this time, then, we 
are about fifteen hours 
in passing through our 
period of daj^, and nine 
hours in rotating 
through our period of 
darkness. Days, then, 
are long and nights 
short in the northern 
hemisphere. The length 
of the day increases as 
one goes northward. 
In London, around June 21, days are 16| hours long; at Stockholm, 
they are about 19 hours; in the north of Norway, the sun does not set 
at all during the greater part of May, June, and July. And thus we 
have here the Land of the Midnight Sun. Likewise Figure 51 shows 
that when the sun is south of the equator, its rays being vertical at the 
tropic of Capricorn, less than half of the tropic of Cancer and of all 
lines parallel to it north of the equator are in the sunlight at one time. 
So that now the days are short, about nine hours in length, and nights 
are fifteen hours long in the northern hemisphere, while in the southern 
hemisphere nights are short and days long. In London the December 
daj'-s are only 7| hours long, and in the middle of the day the height 
of the sun above the horizon is only 15° instead of 62° as in June. 

The Seasons: (i) Inclination of the Earth's Axis. — The 
different positions of the earth in its trip around the sun have a great 
effect on the way in which man lives on this planet. We have seen 
that not only our light but also our heat comes from the sun, and we 
can understand now that this heat is spread during each year over 
different parts of the planet's face. Think of the changes the seasons 
require in our clothing, our food, our games, our modes of travel, 



THE seasons: slant of the sun's rays 53 

and recreations. Think of the effect of the changes on crops, trees, 
furs of animals, and migration of Ijirds. If the earth remained in 
the position of the vernal or spring equinox, the rays would extend 
from pole to pole. As the planet rotated, all places would have 
days and nights of equal length, and throughout the year the dis- 
tribution of heat would be the same. We could have no change of 
seasons. 

If the earth remained in the position it has at the summer sol- 
stice of June 21, since the axis would be inclined 23|°, the north pole 
would always be tipped toward the sun to get its light and heat. The 
Eskimos in the Arctic circle would have daylight forever, and their 
bitter cold climate would moderate. The south pole would be in per- 
petual twilight, and the sun's heat would be felt very little. As heat 
as well as light comes from the sun, it would always be summer in the 
northern hemisphere and winter in the southern. If the axis were 
inclined so that the south pole were tipped toward the sun as on 
December 21, the opposite condition would prevail in each hemi- 
sphere. There would be perpetual night at the north pole and con- 
stant winter for us. Perpetual summer would prevail in the south- 
ern hemisphere and constant daylight at the south pole. 

From Figure 20 we know that the earth's axis always is inclined, 
but owing to another cause of the seasons, we do not have perpetual 
winter or summer in our northern hemisphere. 

The Seasons : (2) Earth's Revolution. — Since the axis is al- 
ways inclined 23|°, it is the earth's revolution that causes first the 
north pole to be turned to the sun and then the south pole. During 
its movement the axis pointing to the Pole star is always nearlj" par- 
allel to any former position. Unless the axis were constantly par- 
allel to its former positions, the change of seasons would not occur. 
The revolution and the inclination of the axis, then, cause different 
portions of the earth's surface to be turned in succession toward the 
sun, and to this fact we can attribute the change in seasons. 

The Seasons : (3) Slant of the Sun's Rays. — Our seasons 
are likewise due to the slant at which the sun's rays strike the earth 
at different times of the year. In Figure 53, A D is a surface on which 
eleven rays coming from the sun fall at right angles. All elevcMi rays 
give light and heat to this surface. But if surface A D is shifted into 




54 THE MOTIONS OF THE EARTH AND THEIR EFFECTS 

the position A C, so that the Hght strikes it at an angle, only six of 
these rays strike it. The amount of heat or Hght received by A C 
is therefore only A of the amount received in position A D. Figure 
5Ji. shows this principle applied to the earth. Eleven rays strike E F 

perpendicularly and give heat to this 

surface. The same number of rays 

are spread over the wider surface 

G H, however, when they strike the 

earth at a slant. The surface G H, 

of course, receives less benefit when 

the same amount of heat must warm 

Fig. 53. Fig. 54. a larger area. When they strike the 

surface perpendicularly, then, the sun's rays are miore .concentrated 

and intense, and have a greater heating effect on the earth. 

We can see the effect of the slant of the tons on our earth by re- 
ferring to Figure 55. On December 21, the midday sun is low in the 
heavens in our region, and its rays reach us at the greatest slant. 
That is the beginning of our coldest season. As the rays become 
more nearly vertical, spring comes, until on June 21 the midday sun 
is high in the heavens, the rays are then most nearly vertical, and 
we receive the greatest quantity of their heat. As the autumnal 
equinox approaches, they slant again and the earth cools. So that it 
is the revolution of the earth, together with the inclination of the 
axis, that causes our seasons by continually changing the slant at 
which the sun's raj^s fall upon us. 

The Zones : Light Belts. — We learned from Figure 51 that 
on December 21, when the north pole is farthest within the shadow, 
the sun's rays are vertical as far south' as the tropic of Capricorn. 
On June 21, when the north pole is farthest within the light, the sun's 
rays are vertical as far north as the tropic of Cancer. That belt 
around the earth between these circles within which the rays are 
always vertical somewhere is called the torrid zone (girdle or belt) 
or tropical light belt. We found the Arctic circle to be the line which 
was reached by the sun's rays at the summer solstice in the northern 
hemisphere and the Antarctic circle to mark their limit during the 
summer season of the southern hemisphere. In these belts the rays 
strike the earth at so great a slant that little effect is made upon the 



SEASONS IN THE ZONES 



55 







earth. These circles mark for us the north frigid zone and south frigid 
zone. The northern belt lies entirely in darkness on DecemlxT 21, 
while the southern belt has sunlight at this time. On June 21, the 
northern belt is 
bright while the 
south frigid zone is 
having perpetual 
night. 

Between the tor- 
rid and frigid zones 
are two belts where 
the sun's rays shine 
every day but are 
never vertical. 
They strike the 
earth, however, at 
less of a slant than 
in the cold belts. 
These are the tem- 
perate zones. Fig- 
ure 56 shows the 
zones marked out 
on the earth's sur- 
face according to the great circles. But it would be quite incor- 
rect to say that there is any sharp boundary between any two of 
them. Many other causes affect climate so that we can find a very 
hot climate in the temperate zones and never-melting snow in the 
torrid zone. The real boundaries are shown by the irregular lines 
in Figure 131. 

Seasons in the Zones. — We must be careful not to imagine that 
the seasons are the same all over the earth. In our north temperate 
zone and in the south temperate, there are the four seasons, spring, 
summer, autumn, winter. In the north and south frigid zones, days 
vary in length from four hours at the time of the (equinoxes to six 
months, and only two seasons are known, summer and winter. In 
the torrid zone, where days and nights are equal, winter is un- 
known; and there are two seasons, the dry and the rainy. In the 



3UNRISE 

E 




SON 



R\S't 



Fig. 55. The daily course of the sun at the time of the 
solstices and the equinoxes. 



56 



THE MOTIONS OF THE EARTH AND THEIR EFFECTS 




Fig. 56. 



southern hemisphere, the seasons are always the opposite of those 
in the northern hemisphere. In this way, north of the equator the 
dry season extends from October till April and the rainy season ex- 
tends from April until October. In the 
belt just south of the equator, these 
seasons are reversed. 

Although the most direct rays of 
the sun fall at noon, the warmest part 
of the day is usually two or three 
hours later. So, although the hottest 
rays fall at the summer solstice, yet 
June 21 is not the hottest part of the 
season. Our warmest weather does 
not come until some time afterwards. 
The earth continues at this time of 
the year to receive more heat during 
the day than it gives up during the 
night. Thus the great heat of a July or August day is not produced 
entirely by the sun of that day, but is an accumulation of the heat of 
the several preceding weeks. For the same reason December 21 is 
not our time of greatest winter cold. The earth continues to lose 
more heat during the night than it receives during the day, and the 
greatest cold does not obtain until some time in January. 

Summary of the Seasons. — Refer to the diagrams and an- 
swer each question, for (1) The spring equinox, March 21. (2) The 
summer solstice, June 21. (3) The autumnal equinox, September 
23. (4) The winter solstice, December 21. 

(1) How do the poles lean with reference to the sun? 

(2) Where do the northernmost and southernmost rays of the 
sun fall? 

(3) On what circle of the earth are they vertical? 

(4) What is the length of day and night? Where are they longest? 
Where shortest? 

(5) What season is it in the northern hemisphere? In the south- 
ern? In the five zones? 

QUESTIONS. — (1) Suppose the earth rotated on its axis but did not revolve 
around the sun, would we have day and night? (2) Tell what the result would be if the 



EXERCISES 57 

earth had no motion of rotation on its axis but merely revolved about the sun. (3) If the 
earth's axis were perpendicular to the plane of its orbit, how would the length of day and 
night be affected? (4) Tell about the seasons of the earth in this ease. (5) Why did 
people once believe the heavens moved and that the; earth was stationary? (6) State the 
cause of the zones. (7) Tell the simple meaning of zone, koInHcc, equinox, equator. 
(8) What are the effects of the earth's revolution? (9) Tell in what way the change of 
the seasons affects your games and exercise. (10) How do the seasonal changes affect a 
farmer's life? A bricklayer's work? A storekeeper's business? A steamship captain's 
duties? (11) At what time does your shadow always point directly north? (12) At 
noon on December 21 how would a man's shadow be cast if he stood at the equator, 
Cancer, Arctic circle? (13) On June 21 at these points? (14) What would be the effect if 
the earth's axis were always in the position shown in Figure 491 In Figure 60? In Figure 
61"! (15) If the earth revolves at such great speed why do we not notice it? (IG) What 
changes do the Eskimos notice in the sun's position every year? (17) Give two causes of 
our change of seasons. (18) Why are the sun's rays more intense when it is high in the 
heavens than when it is lower? (19) Arc the sun's rays ever vertical at New York? 
(20) On what day does the sun appear farthest north? (21) From Figure G2 find how 
many miles we are from the tropic of Cancer. (22) Which way does the sun seem to bo 
moving on June 25? Why? (23) Make a list of all the large countries in the north tem- 
perate zone. The south temperate zone. (24) What season are people having now in 
the south temperate zone? (25) Should you expect to find a very great change in 
temperature in crossing the tropic of Cancer? (26) Suppose the earth rotated once 
every ten hours. What effect would you note? (27) Suppose a rotation required fifty 
hours; tell all the effects you can think of. 

EXERCISES. — (1) Draw a two-inch circle and show day and night as it would be 
on March 21. (2) Write a paragraph explaining why we have four seasons. (3) Place 
in your notebook your observations on the length of the days for one week. Are they 
gro'rt'ing longer or shorter? (4) Make a table under your observations showing in which 
months they grow longer and in which shorter. (5) Keep for a week a record of the length 
of your shadow when you stand on the same spot at 8:30, 12:30, and 5 o'clock. Explain 
the changes. (6) Make a diagram to show the earth inclined to its orbit 45°. (7) Make 
a diagram showing four positions of the earth when the axis is perpendicular to the orbit. 
(8) Where would the tropics be if the axis weie inclined 45°? Where would the polar 
circles be? (9) How would the heat and cold compare with what we now feel? (10) What 
other effects can you think of? (11) Make a diagram of the earth with its axis parallel 
to the plane of its orbit. What effects might be observed should this change take place? 

(12) How much should the axis be inclined to bring the tropic of Cancer to New York? 

(13) How much should it be inclined to bring the Arctic circle to New York? (14) Why 
is the heating effect of the vertical rays of the sun greater than that of the slanting rays? 



CHAPTER V 



LATITUDE; LONGITUDE; TIME 










ST^ 



w 



ZJ 



2 E 



Directions on the Earth. — From the fact that the earth 
rotates on its axis, men have been able to determine for us certain 
chrections on its surface. We know that it turns toward the east or 
the " dawn-point " and that the opposite direction is the west. We' 
know that the Pole star remains fairly constant over the north pole 
of the earth and that the opposite direction is the south. If we 
stand with extended arms facing east, our arms will be parallel T\ath 
the earth's axis. Our left arm vnW point north, our right arm, south. 
It is rather easy to locate a house in a city like New York. We 
know that one avenue, Fifth, has been selected to divide the Borough 
^ of INIanhattan into an 

}={ FnjF J r^l^sTT ^ I r^ r-|; east and a west side. 

So that if a man says 
he lives on Third 
avenue, we know at 
once on what side 
from Fifth avenue he 
hves, and that to 
reach his house we 
should have to walk 
four blocks east from 
the di\'iding avenue. 
But we should also 
need to know on what part of Third avenue his house is to be found. 
We see that in order to determine this question the city has been 
divided also by streets which run east and west. Thus if this man 
lived on the corner of Third avenue and East 32nd street, we should 
know not only that his house was east of a certain dividing line 
but also north of a certain other line. We should then ride up 
thirty-one blocks from 1st street to see him. 

58 



■zffzrniL 



3 ei 



Jr27T 



^?L 



g 26T«— |Op 



3^ 



p25T-H-) p 



l^iH 



liililZl c 



paBD — [ r- 



|f2?ND— I 



HE] 










3 Q\ — tTo cziKiz!!] [E:iaS[:z 

s 



Fig. 57. Map of a part of a city, 



LATITUDE 



59 



Latitude. — We might compare the earth to a great city. The 
equator, Uke a middle street, divides it into a north and a south part, 
while many circles running east and west like streets divide the hem- 
ispheres into smaller sections. These circles running parallel to the 
equator are called parallels of latitude. 

In a circle there are 360 equal divisions called degrees. In the 
circumference of the earth passing through the poles and in the equa- 




FiG. 58. Degrees of latitude and parallels by means of which points are located on the 
earth as north or south of the equator. 

tor also there are then 360°. Since the equator divides the earth into 
two hemispheres, there are 180° in each hemisphere. Between the 
equator and the poles there are 90°. The distance north or south 
from the equator, measured in these degrees is latitude. Each of 
these 90 degrees of latitude measured on the earth's surface, would 
be about 69 miles in length. San Francisco is near the 38th degree 
of north latitude, while Rio de Janeiro is 23° south latitude. 

The latitude of a place is most easily found by locating the posi- 
tion of the Pole star. The North star appears in the northern hori- 
zon to a person standing on the equator and the Southern Cross is 
seen nearly on the southern horizon. To an explorer at the pole the 
North star appears directly overhead. At every point between there 
would be a different angle between the plane of the horizon and the 
Une from the observer's eye to the North star. In the northern hem- 
isphere the latitude may be found by measuring this angle between 
the Pole star and the horizon. 



105 Longitude 10 




EXERCISES. — (1) Give the extent of the United States in degrees of latitu 
In degrees of longitude. (2) Name the states whose boundaries are fixed by parallels 
meridians. (3) Give the approximate latitude of St. Louis, San Francisco, Mob 
Helena, and Duluth. (4) Name the states through which the 40th parallel of no 
latitude passes. (5) The 85th meridian of west longitude. (6) Give approximate h 
tude and longitude of St. Paul, New York, Boston, Kansas City, and Seattle. (7) 




itllc drifts from 27° north latitude, 92° west longitude to .34° north l:ifitud(-, 7.i° west 
ntcitude. Trace its course on the map. (X) Locate in latitude and lonnitude (^uehec, 
iimipeg, Los AnRcles, and Austin. (9) A vessel passes from 47° norfii latitude, 92° 
~t lonuitude to 29° north latitude, 94° 30' west longitude. Name the waters through 
hicli it steams. (10) A derelict drifts from 40° north latitude, 129° west lonjiitude to :W° 
irth latitude, 110° west longitude. Trace its course and determine its present position. 



62 



latitude; longitude; time 



Since parallels are at equal distances apart all over the world, 
we can use latitude to measure distance. We can say, for example, 
knowing the latitude of San Francisco and Rio de Janeiro and also 
the fact that a degree of latitude is the equivalent of sixty-nine miles, 
that the Brazilian capital is 945 miles nearer the equator than is San 
Francisco. 

Longitude. — It might be very well to know that a city we are 
seeking is in latitude 40° north, but since this parallel extends around 

the earth, the task of locating the place 
would be hopeless. It would be like tell- 
ing a person that a man could be found 
in 32nd street. Some means must be 
found for locating places east and west 
on these parallels. Other imaginary lines 
are used. These great circles which ex- 
tend around the earth through the poles 
are called meridian circles, and each of 
the semicircles, extending from pole to 
pole, a meridian, or midday line. 

Any avenue in New York, might have 
been chosen as well as Fifth avenue to 
divide the city into an east and a west 
side. The important point is that every- 
body accepts the same avenue as the 
dividing line. The same thing is true of these meridians. In this 
way the great circle passing through Greenwich at London, in Eng- 
land, has come to be accepted as the dividing line on the earth 
between eastern and western hemispheres. Greenwich was chosen 
because there was situated there a large observatory, fitted with 
telescopes and various other instruments by the aid of which the 
stars and planets were observed and very important facts about our 
universe discovered. So England thought this a fitting place from 
which to begin the numbering of the meridians. The Greenwich 
meridian is called the prime or "first" meridian; and its opposite 
meridian, 180° east or west from Greenwich, is called the sub- 
meridian. In the northern hemisphere the sub-meridian passes near 
Rat island, one of the Aleutian group belonging to the United States; 




Fig. 60. Great and small circles. 
Notice that all meridians meet at 
the poles and that parallels of lati- 
tude are smaller and smaller the 
farther they are from the equator. 



QUESTIONS 



63 



and in the southern hemisphere it passes near the Fiji ishmds which 
belong to Great Britain. 

As shown in Figure 01, degrees are designated east and west frcjm 
this prime merithan. A.i\y place, like Buffalo, 79° west longitude. 





'vctrj^ \yooso'7croffscrjo'jo'20' icr & jcrio'jo'^o'jcroffTtracritcrJ^ 




Fig. 61. Degrees of longitude and meridians by means of which points are located as 
east or west of the prime meridian. 

is 79° west of the prime meridian; while Paris, 3° east longitude, is 
3° east of the meridian of Greenwich. Longitude is distance east or 
west from the prime meridian, measured in degrees. The circles 
that form the meridians are called circles of longitude. Since these 
are drawn 1° apart there are 360 meridians. You notice in Figure 61 
that they are numbered from 1° up to 180° in both directions from 
the Greenwich meridian. The prime meridian itself is 0° longitude. 
At the equator a degree of longitude measures 09 miles. As the 
meridians approach the poles they draw closer together, so that this 
measure constantly decreases. At the 20th parallel of latitude a 
degree of longitude measures about G5 miles, at the 80th parallel, 
about 12 miles. 



QUESTIONS. — (1) How can all places on the earth he located in a north and south 
direction? (2) In an east and west direction? (3) Why are meridians not parallel to 
one another? (4) How many degrees of latitude arc found between the poles? (5) What 
is the length of a degree of latitude? (G) Why was the meridian of Greenwich chosen as 
the i)rime meridian? (7) Explain why the people of Uruguay are never able to see the 
Pole star. (8) What uses arc made of parallels and meridians? (9) What is meant by 
sub-meridian? 




EXERCISES. — (1) From the map give the approximate latitude and longi- 
tude of Rome, Havana, Paris, and Calcutta. (2) Find cities around the earth near the 
42nd parallel of north latitude. (3) A derelict drifts from 40° north latitude, 20° west 
longitude to 5° north latitude, 40° west longitude. Trace its course on the map. (4) Give 
the approximate latitude and longitude of Cape Town, Bombay, St. Petersburg, and 
Cairo. (5) What place is located at 25° north latitude and 81° west longitude. (6) Name 
eight large cities from which the Pole star can be seen. (7) Name all the countries 
through which the 30th parallel of north latitude passes. (8) The 30th parallel of south 
latitude. (9) The 60th meridian of west longitude. (10) Find as many places as you 
can where parallels and meridians are used as boundaries. (11) Find five cities with 
the same approximate latitude as New York. (12) What islands are situated near 15° 



} J*.i\noroio 




Cape 



iPortugal SIB Ua\} 

I I Kr.in,-,^ 1 I spnln ^"■'* Dcniuarlt 

r i n»r.nnnj I 1 \nll..rlnn.l. 1 I Inll,-.! SlalM 

llif Davlgal-lc portlono of pIt . 

- btcaojBbij. RuuttB. Fipureb inJlcato dietancea in 
gtograpliical inilos between places luarkuil thus: 
' Kallioade and telegraph llnei. 
SubmariDe cables and telegraph llD«a. 
CaraTan Kflutea.- I 

Canala. 



Grienwich 00 



0° Lonpitudo K.-i»t :iu' from firctnwi^liiit)' 



lorth latitude and 120° oast loiiKitudc? (13) A bottle drifts from 3')° north latitiido, 
L50° east longitude to 45° north latitude and 135° west longitude. Trace its course on 
;ho map. (14) Give approximate latitude and longitude of Christiania, Vancouver, 
Brisbane, and \'alparaiso. (15) CJivc the approximate latitude and longitude limits of 
^''cnezuela, Alaska, and Persia. (IG) If a vessel sails from l.'5° north latitude, 80° east 
ongitude to 52° north latitude, 0° longitude, through what waters will it pass? (17) A 
:Dark made the run from .35° .south latituile, 50° west longitude to 35° -soutii latitude, 140° 
5ast longitude, a distance of 10,000 miles in thirty-eight days. Find these two porta and 
ietermine her average daily run. (IS) Determine the latitude and longitude of Berliii, 
Hongkong, Naples, Peking, and Buenos Aires. 



66 



latitude; longitude; time 



The Division of a Degree. — On a very large map of the state 
of New York, the circles of latitude would be too far apart to be of 
much use. Likewise the circles of longitude. It is customary to 
divide each degree into sixty equal parts called minutes. Each min- 
ute is in turn divided into sixty equal parts called seconds. In this 

way a degree of latitude may 
be measured by 3,600 parts 
and accordingly a place can 
be located with more accur- 
acy. The degree sign is °; 
the minute sign '; and the 
second sign ", Thus the loca- 
tion of the city of New York, 
40 degrees, 45 minutes, 23 
seconds, is marked 40° 45' 
23", north latitude. This line 
passes through the grounds 
of Columbia University. 

Importance of Latitude 
and Longitude. — Latitude 
and longitude are very impor- 
tant, especially in locating 
spots in the great plains or 
on the ocean, where no one 
would know his position on 
the earth unless he could cal- 
culate it from the stars. Ship 
commanders find their lati- 
tude and longitude daily, 
plotting the position of their 
vessel on large charts. Every- 
one who uses maps makes use 
of latitude and longitude, 
because all maps are drawn to show the positions of places in the 
world by their latitude and longitude. The parallels and meridians 
are further used as state or international boundaries and even for 
laying out the streets and lots of a city. 




Fig. 63. A map showing 
of latitude and longitude. 



minutes and seconds 



THE COMPASS 



67 



Meridians and the Sun. — We said that meridian meant 
" midday " line. When the sun is just above a north-south Hne pass- 
ing through New York, we say that it is noon in New York. This 
line would pass, if extended, through the two poles. The earth must 
rotate on its axis before the sun reaches our meridian again, twenty- 
four hours later. Every place east or west of us is on a different 
meridian from ours, and has its noon at a different time, since the 
sun cannot be over more than one meridian at a time as the earth 
rotates beneath it. All meridians to the east of us get the sun or have 
noon before we do, and places to the west have theirs later. We have 
already learned that there are 360 meridians. 

Longitude and Time. — Since it takes the earth twenty-four 
hours to make a complete rotation on its axis, the sun in that time 
seems to pass over 360° of the earth's circumference. In one hour, 
then, the sun seems to pass over one twenty-fourth of 360°, or 15° 
of the earth's circumference. If this is true, points which are 15° 
apart will vary in time by one hour. In the United States, for ex- 
ample, the sun's rays fall upon the Atlantic 
coast more than three hours sooner than 
upon the Pacific coast. The reason, of 
course, is that the earth rotates from west 
to east. When New York boys and girls 
are going home at three o'clock, pupils in 
San Francisco are just being dismissed for 
luncheon, since the sun shows that it is only 
twelve o'clock in the western city. When 
San Franciscans are reporting to school at 
nine o'clock. New Yorkers are going home 
for luncheon. 

The Compass. — On the bridge of every ship in plain view of 
the steersman a compass is always found. This instrument is of 
great importance in determining directions on the earth. It con- 
sists of a bar of magnetized steel or of several needles so suspended 
that the bar or the card to which the needles are attached will swing 
freely in a horizontal plane. It is constructed of a copper or brass 
bowl, hemispherical in shape, into which is mounted the compass card 
fitted upon a delicate point, the dial revolving upon an agate cap to 




Fig. G4. A pocket compass. 



68 



latitude; longitude; time 



insure its working easily. As the roll 
and pitch of a vessel would be liable to 
unsettle the ordinary compasses, these 
bowls are usually fitted with some alco- 
holic liquid to keep the card steady. The 
needles always point north and south, 
regardless of the position of the ship. 

The compass does not point to the 
geographical pole but to the north mag- 
netic pole in northern Canada (70° north 
latitude, 97° west longitude). By know- 
ing how much the compass varies from 
the true north, however, the direction of 
the north pole can alwaA^s be learned. 
The amount of this magnetic variation 
is called declination, and the navigating 
officers of vessels are alwaj^s provided 
with goverimaent charts which show 
the exact amount of dechnation they 
have to 
make 
allowance for anywhere on the 
earth. Without the compass, 
navigation on the seas would be 
almost impossible. A land compass, 
much smaller than a ship's compass, 
is of great value to explorers, lumber- 
men, hunters, and survev'ors. 

Longitude at Sea. — The navi- 
gating officers when at sea are care- 
ful every day to take the elevation 
of the sun with an instrument called 
the sextant. In this way thev^ 
can tell when it is exactly noon 
wherever they may be. Ev^ery 
ship carries a chronometer or clock ^^ gg ^^^^^^ ^^^^^ ^^^ ^^^^^^^ 

which giv'es Greenwich time. By of the sun by means of the sextant. 




Fig. 65. A ship' 
compass stand. 



binnacle or 





THE INTERNATIONAL DATE LINE G9 

means of this time, the officer can learn how far east or west of 

the prime meridian he is, or in other words he can get the 

longitude of the ves- ^^^/^^^ 

sel. For example, "■ 

suppose the Green- ....*. /^^^C^*!!^/?^!!! 

wich time is 8 o'clock >-r - ""^/H^^^^ 

and the ship's time pi \ '"" 'Ti/\ o/w 

12 o'clock. There is .^^^rpenJicu/grRax.....^^ /C ^^ 

a difference of four ^ *\^ f / ^ 

hours. Since a differ- 2 

ence of one hour in - '^\^1^=iu:l_^-J:-4^^ 

time corresponds to iy.~V™/™™™J.".". 

a difference of 15° in , ■♦ • 

. rio. G/. inc time on dmcrcnt meridians wlicn it 1.5 

longitude, this ship noon on the prime meridian. 

must be in 60° east 

longitude. The longitude is east because the time by the sun i.3 
later than the time ]jy the chronometer. If these facts were re- 
versed, the longitude would be 60° west. 

A Table of Longitude and Time. 

360° of longitude corresponds to 24 hours of time. 
15° " " " " 1 hour " 

r " " " " Vf hour or 4 minutes of time. 

15' " " " " 1 minute of tiitic. 

1/ (( (( It II 1 U <( II 

15" " " " " rtecond " " 

^ 1 5 

The International Date Line. — If a man starts westward from 
Greenwich to travel around the world, he must set his watch back one 
hour for every 15° of longitude passed over if he wishes to have the 
correct local time. This would require twenty-four changes during 
the journey around the world and thus he would lose twenty-four 
hours, or a whole day. 

If he starts eastward from Greenwich, he would set his watch 
ahead twenty-four times to have correct local time and thus he would 
gain a day. 

"As we pass to the ca.st, the tunc dotli iiu'roa.so; 
As wc pass to the west, the time iluth grow less." 



70 latitude; longitude; time 

To overcome such differences of the extra day, the nations in 
1884 agreed upon a place where time shall be changed. That place 
is the 180th meridian east and west from Greenwich, or the Inter- 
national Date Line. This line has been drawn so that no two neigh- 
boring regions belonging to the same country shall have different 
dates at the same time. This accounts for its irregularity on the 
map. Suppose that two men start from Greenwich, one going east- 
ward and the other westward. The one traveling eastward will find 
the time at the ISOth meridian twelve hours later than when he 
started, while the one traveling westward will find the time there 
twelve hours earher. So the latter on crossing the line on Sunday 
must call the day jMondaj'; while the one traveling eastward in 
crossing the line on ]\Ionday must call the day Sunday. 

The International Day begins immediately after the stroke of 
midnight in London. The sun is then passing the meridian of 180° 
and it is noon at Rat island. Suppose that midnight of December 
31 has arrived in London, and im mediately January" 1 has begun 
there. Is it, at Rat island, the noon of December 31 or of Januarj^ 1? 
We know now that it is the noon of December 31 until the sun reaches 
the 180th mericUan. Immediately upon the sun's passing that merid- 
ian, it is the noon of Januarj^ 1 at the edge of the eastern hemisphere; 
and it becomes noon at each successive meridian as the sun reaches 
it, till the 180th is reached again twenty-four hours later. Locate 
the International Date Line on the map on pages 64, 65. Between 
Berlin and London a change of date from December 31 to January 1 
would work confusion; none is likely to arise between the Primorsks 
and the Alaskans, nor between the Aleuts and the Kamchatkans, 
neighboring people having different dates and little commerce. 

It is interesting to know that the Fourth of July begins at Guam 
island in the Pacific at about 9:30 a.m., and at ^Manila at 8 o'clock 
in the morning of the International Day. It is then 7 p. :m. of July 3 
in Xew York. The New York boy, then, is not far ahead of time 
when he begins to celebrate the Fourth at 7 o'clock the evening 
before. 

Standard Time. — We saw that a difference of 15° in longi- 
tude between two places corresponded to a difference of one hour in 
time. If you traveled from Xew York to St. Louis, you would find 



STANDARD TIME 



71 



that your watch was one hour fast in that city. If you went on to 
Denver, you would find your watch was two hours too fast, while 
at San Francisco your time would he three hours ahead of tiie time 
of the clocks in the western city. Each place in between these cities 
would also have its own local time, or sun time. When the sun is 




Fig. 68. 



in the meridian of any town, it is 12 o'clock, noon, and at all places 
east of that line, it will be later and at all places west of it, earlier. 
The time of cities a few hundred miles apart, east antl west, used to 
differ in this way by twenty minutes, thus causing great confusion in 
time-tables and train management. Starting westward with Boston 
time, trainmen found a time different from their own at Albany, at 
Buffalo, at Detroit, and at Chicago. Travelers' watches were always 
wrong. To avoid this difficulty, our continent has been divided into 
belts, and hour-meridians were selected, 15° apart, as shown in Fig- 
ure 68] and within each hour-belt the time of the central meridian 
was adopted l)y all the towns and the railroads. These divisions are 
called Standard Time Belts; the Atlantic, central meridian (30°; the 



72 latitude; longitude; time 

Eastern, 75°; the Central, 90°; the Mountain, 105°; and the Pacific, 
120°. Atlantic time is four hours earlier than London time, and 
Pacific time is eight hours earlier. In going from New York to Chi- 
cago, the traveler sets back his watch one hour from eastern to cen- 
tral time. If he starts from New York at 12 o'clock, in twenty-four 
hours he reaches Chicago at 11 o'clock, when the sun has just reached 
the meridian of New York and one hour before it will reach the 
meridian of Chicago. On his return, if he reaches Pittsburg at 12 
o'clock, central time, he immediately starts for New York at 
1 o'clock, eastern time; for every 15° difference the watch is set one 
hour ahead. 

The boundaries of the time belts are irregular, because time is 
not changed on crossing the margin of a belt but at the nearest im- 
portant railway center. In passing from eastern to central time, 
the change is made at Buffalo, Pittsburg, or Atlanta, as these are the 
principal cities that lie on the boundary between the eastern and the 
central time belts. Railway time-tables show a change of one hour 
at these points. 

STANDARD TIME OF THE WORLD. — In 1913, at the International Con- 
ference of the Hour, the delegates of twenty-four countries met in Paris to sign an agree- 
ment establishing a standard time of day for the whole world. They decided on Paris 
as the point from which reckonings are to be made. 

The idea is the same as the one we studied as United States Standard Time. The 
globe will be divided, as shown in Figure 69, into twenty-four sections, each named by 
a letter of the alphabet, and each corresponding to a difference in longitude of 15 degrees. 
In this way the difference in time between any two adjacent sections will be one hour. 
Section U in which Paris is situated will be taken as the one from which standard time 
will be measured. Every day at midnight and at 10 a. m. Paris will send out wireless 
signals all over the world. This will be of great benefit to navigators, since for the first 
time in history they will be enabled to correct errors in their chronometers and thus 
determine the position of their ships with a greater degree of accuracy than has ever 
been possible before. 

In addition to the signals from Paris, others will be sent out at different hours from 
other stations. Some of the latter, including that at Norddeich, Germany, are already 
in operation. It has been arranged that signals shall be flashed from these other stations 
at the following hours each day: Arlington observatory, U. S. A., 3 a. m. and 5 p. m.; 
Manila, 4 a.m.; Mogadiscio, Somali coast, Africa, 4 a.m.; San Fernando, Brazil, 2 A. M. 
and 4 p. M.; Timbuktu, 6 a. m.; Norddeich, Germany, noon and 10 p. m.; Massaua, Africa, 
6 p. M. ; San Francisco, 8 p. m. Navigators, explorers, and others will be able to get the 
exact standard time from one of these stations at least once a day. 

Beginning at 9:57 a.m., twenty warning signals will be sent out by wireless, the 
last one ending exactly at 10 a. m. When the last signal is picked up by a wireless 



QUESTIONS 



73 



apparatus anywhere in the world the operator will know that it is exactly 10 a. m. by 
standard time in Paris. 

We have seen how the distance traveled by a ship each day is found by comparing 
the local or ship's time with Greenwich time, the ship's time being determined by tho 
position of the sun or stars and the Greenwich time by the vessel's chronometer. From 
this it will be noted that the difference east or west between any two places is merely 
the difference between the two local times expressed in degrees. No way has ever been 
found, however, for making a ship's chronometer keep exactly correct time. At times 




yjHek If 1^ NOON in secTiON \j the time /a/ th£ orneR seen on s /sj 
liP| 2^-3^1 *^ 5^1 tf-^\ 7---^ 8^1 9«) 10^ ll--=|NOON i-=^| Z-rj sr^j 4~| 5-| 6-^ ■r-\ 6'='| 9'--] (C ^; I l^ly,' ' 
TSsS — i55» — IB»: — BU" — ISS"^ 55" T5» 55» — 1!» RJ r5» 5» r5= SS» — TfS' — So* tj- m- io^ luT- " 



XZ^^£f^ 



Fig. 69. A map showing the proposed standard time belts of the world. 



the clock's error is such as to render the accurate finding of the ship's position impossible; 
and in such cases when the vessel is near land, disastrous results may follow. With tho 
scheme of the International Conference the wireless signals will act as a check on tho 
chronometers. The great importance of this may be realized when it is remembered 
that an error of one second in calculating the time at sea means an error, in determin- 
ing the ship's position, of something like 1,000 feet. 



QUESTIONS. — (1) Why is it necessary to divide degrees of latitude and longitude? 
How are they divided? (2) Explain the importance to man of latitude and longitude. 
(.3) When it is noon at New York, what time is it on a meridian 15° to the west? To 
the east? (4) When it is noon at Charleston, South Carolina, what time is it at Pitts- 
burg? (5) Wlicn it is sunrise in New York, is it before or after sunrise in Buffalo, Gal- 
veston, Los Angeles? (0) How many hours elapse while a i)oint of the earth's surface 
turns through 3G0°? l.SO°? 90°? 30°? 15°? (7) Of what u.se is the compass to man? 
(S) Describe the compass you would see on a .shij/s bridge. (9) How does this differ 
from a pocket compass? (10) Why was the International Date Line estal^lished? Why 
is it not straight? (11) Name the time belts in America and locate each. (12) How 
is the time for each determined? 



74 latitude; longitude; time 

EXERCISES. — (1) When it is 7 o'clock in the morning in New York, what 
time is it in Chicago? In San Francisco? In Manila? In Rome? In London? (2) 
When it is noon by the sun, a ship's chronometer shows the time at Greenwich to be 
4 o'clock. Find the ship's longitude. (3) Suppose at noon the chronometer shows the 
Greenwich time to be 6:30 a. m. What is the longitude? (4) What time is it now at 
Greenwich? At Buenos Aires? At Tokyo? At Colon? At Panama? (5) If you were 
going home from New York to Salt Lake City, where would j^ou change the time of your 
watch? (6) Where and how much would you change your time in traveling from Los 
Angeles to Chicago? 



CHAPTER VI 



THE MOON; ITS REVOLUTIONS AND PHASES 



Facts about the Moon. — In Chapter I we referred to the 
fact that when our universe was in process of formation many ages 
ago, the satelhte known as the moon was thrown off from the earth. 
Astronomers tell us that the moon, if forced into the same shape, 
would quite fill the great gash in our planet's face: the bed of the 
Pacific ocean. The moon's diameter is about 2,160 miles, and Figure 
70 shows us the circumference 
of the satellite as compared with 
the size of Europe. We must 
not be confused by the apparent 
size of the moon, which often 
seems to be the largest of all 
heavenly bodies visible. The 
fact is, however, that the moon 
is the smallest of all the heavenly 
bodies visible to us, the stars ap- 
pearing very small on account 
of their great distance. In 
shape it is spherical like the 
earth, and it, too, is slightly flattened at its poles, due to its rotation. 

A cord long enough to be wrapped ten times around the earth at 
its equator, would be long enough to reach from the earth to the 
moon. A railroad train which could encircle the earth in twenty- 
seven days could, if going at the same speed, reach the moon in 
thirty-eight weeks. This distance is about 240,000 miles, as an aver- 
age. But, just as the earth's orbit around the sun is not a perfect 
circle but an ellipse, so the moon's orbit is an elliptical i)ath and its 
distance from us varies from 253,000 miles to 222.000 miles. Tiie 
size of the moon is one-forty-ninth that of the earth, but our planet 




Relative size of Europe and the 



76 



THE moon; its revolutions and phases 



is eighty times heavier. It would take forty-nine moons united to 
form a globe as large as ours. 

Surface of the Moon. — When the satellite is viewed through 
a telescope as shown in Figure 4, large flat areas are seen which some 

people think may have been the 
beds of seas in ancient times. We 
can see them with the naked eye 
as irregular dusky regions. Nearly 
two thirds of the surface, as we 
see it, consists of bright regions, 
which are broken and mountain- 
ous. The mountains of the moon 
generally surround enormous pits 
like volcanoes, as shown in Figure 
71, but these differ in their great 
size from our volcanoes, since 
many are sixty miles across. In 
addition to these circular moun- 
tains there are several long and 
lofty ranges of moon mountains, 
very much like our Andean and 
Himalayan ranges. 

We are unable to discern any 
trace of air or water on the moon, 
and we suppose consequently that there is no form of life on this great 
wanderer. The only changes seem to be those between heat and 
cold, and light and darkness. The moon, like the earth, has no light 
and little, if any, heat of its own; but its surface acts as a huge mirror 
in the sky and reflects or sends back, as Figure 73 shows us, the light 
received from the center of the solar system. 

We on the earth are never in a very great danger of being " moon- 
struck " since the light reflected from this mirror in the skies is only 
6,0000 ^^ strong as sunlight. 

The Moon's Revolution and Rotation. — The earth is a sat- 
ellite of the sun and the moon is a satellite of the earth. Just as the 
sun holds the earth in its orbit and forces it forever to swing around 
the parent body, so the earth through the force of gravitation holds 




The mountainous surface of the 



PHASES OF THE MOON 



77 



the moon in leash, and compels its satellite 

to make the circuit of its orbit once in 

every 29| days. It was the revolution of 

the moon around the earth in this period 

that formerly gave rise to the custom of 

measuring time by months (moons). As 

the moon revolves about the earth it also 

rotates on its axis, but, strange to say, it 

rotates so slowly that it requires 29| days 

also to complete even one rotation. We 

know that the much larger earth spins 

around on its axis once in every twenty- 
four hours. As a result of this condition, 

the length of a day on the moon is about 

that of one of our months, and the whole 

lunar year has onh^ twelve days. 

Place a spot of ink on a lead pencil 

and then revolve the latter around a 

book, the ink mark facing the book. 

Turn it on its axis so that, like the moon, 

it rotates once while making its revolution. 

You will notice that the spot of ink all during the trip continues to face 

toward the book. In doing this you have illustrated the monthly 

revolution of the satellite around the earth and its rotation in the 

same period of time on its axis. Our moon then turns the same face 

toward the earth. We al- 
ways see the same " man 
in the moon," an appear- 
ance which is really the 
bottoms of dried seas. No 
one on the earth has ever 
seen the other side of the 
moon, and yet we know from 
the shadow it casts that the 
plan(>t must be spherical. 
Phases of the Moon. 



■ 


B^g 


■ 


'■^^ 


w 


" ''^IH 


f 




i<. ^ 


■^^r^^^^ 


f 


.-...v. 1 


L 




■ 


^Zi^l 



Fig. 72. The moon at the first 
quarter. 




.5. How tlic moon sends us its liglit. 



— As the moon travels 



78 THE moon; its revolutions and phases 

around the earth it shows itself, by the reflected hght of the sun, in 
different forms. These are gradually changing from one shape into 
another and are known as the phases (appearances) of the moon. If it 
shone with light of its own, it would always appear circular to us, as does 
the sun. But we have every month the changes you have noticed, a 
new moon, quarter moon, half moon, and full moon. These phases 
are due to two causes: First, to the fact that the moon is opaque 
and can therefore be lighted only on one side at a time, as the eight 
positions of the moon in its orbit show in Figure 74- The second 
cause is the fact that the earth's orbit and the moon's orbit are not 
in the same plane. The moon's orbit is inclined to the earth's at 
an angle of over 5°, so that the moon may be on the same side of 
the earth as the sun and not be on the straight line connecting 
them. If you can imagine the sun in this diagram to be shining 
through the book from a point several feet behind it, you can see that 
all three bodies will not be in the same straight line. The moon 
therefore will be very unequally lighted up in its revolution around 
the earth. 

1 . The New Moon. — When the moon is in that part of its 
orbit which passes between the sun and the earth, as in 1, it has its 
back turned toward us, the illuminated side being toward the sun. 
It is then invisible, and this appearance is the true '* new moon." 
However, we always give this name to the narrow crescent-shaped 
figure, which shows in the west, after sunset a few days later, 
as in 2. 

2. First Quarter. — The crescent gradually enlarges into a half 
circle as the moon passes away from the sun and we see more of its 
lighted face. This half-circle appearance or phase, which occurs 
when the moon arrives at a position in the sky at right angles to the 
direction of the sun at 3, is called the *' first quarter." 

3. Full Moon. — The moon in 4 begins to move around behind 
the earth so that our planet is between it and the sun. No light at 
all now would reach the moon except for the fact that since the orbits 
are not in the same place, the sun, earth, and moon are not in a 
straight line. When the satellite has arrived just behind the earth 
its whole face, lighted up, is turned toward the earth. This phase, 
number 5, is called "full moon." 



THE HARVEST AND HUNTER 's MOON 79 

4. Last quarter — Now the moon returns around the other 
part of its orbit so that, at 6, its face grows smaller and, at 7, it 
assumes the appearance of a half circle. This is the ** last quarter." 
Then comes, at 8, the crescent shape again or " old moon," and finally 




Fig. 74. The phases of the moon. The outer circle shows the moon as seen from the 
sun. The inner circle shows the moon as seen from our earth. 

it disappears to become a new moon once more. This trip has taken 
it just 29^ days. 

You can imitate the moon phases very clearly by taking an orange 
and placing yourself several feet from an unshaded lamp. Sit on a piano 
stool in order to turn more easily. Hold the orange up in the light 
and cause it to revolve around you by turning yourself upon the stool. 
As it passes from the dark position between you and the lamp, you 
will observe the crescent new moon, the quarter, the full, and finally 
the old moon. 

The Harvest and Hunter's Moon. — These full moons, which 
in some parts of the world give a helpful light after sunset, occur only 



80 THE moon; its revolutions and phases 

near the time of the autumnal equinox. The one nearest the date 
of the equinox, September 23, is the " harvest moon/' and the full 
moon next following in October is the " hunter's moon." For sev- 
eral successive evenings they rise immediately after sunset almost at the 
same hour. This is due to the fact that the plane of the earth's orbit, 
from Avhich the moon's path departs only by 5°, is, in the high lati- 
tudes, nearly parallel with the horizon. 

We learned that in our winter the sun is low in the sky, being 
south of the equator. Since the full moon must always be opposite 
to the sun, it is always higher in the sky in winter and gives a brighter 
light then, than in summer. 

Eclipses of the Moon. — You have noticed in Figure 74 that 
there are times when the moon enters a position between the sun and 



Fig. 75. An eclipse of the moon. 

the earth, and times when the earth in turn shuts off the moon from 
the sun. Sometimes these positions of the bodies cause an eclipse 
or a " leaving out of light." You see from Figure 75 that the opaque 
earth throws out a long conical shadow into space on the side away 
from the sun. The moon in its orbit must pass through the dark 
space in its monthly trip. While in the shadow, it receives no light, 
and is said to be in eclipse. These lunar echpses would occur every 
month if the sun, moon, and earth were on a straight Hne, but as we 
have seen, the moon's orbit is inclined 5° to that of the earth. They 
occur only at time of full moon, and according to the deviations of 
the earth, the sun, and the moon from a straight line, the moon may 



ECLIPSES OF THE SUN 81 

pass through the center of the shadow, or to one side of the center, 
or merely dip into the Ught edge of it. When it passes through the 
dark middle and is entirely covered we have a total eclipse. When 
only a part of the moon is darkened we have a partial eclipse. A 
total eclipse often lasts two hours and is visible from all parts of the 
earth then facing the moon. 

Eclipses of the Sun. — • In this case the moon causes the eclip.se 
by hiding the sun from the earth. Here again, to have an eclip.se 
the three bodies must be in a straight line drawn through their cen- 
ters. The moon often passes between earth and sun, above or below 
this line, so that no eclipse occurs. However, an eclipse may occur 
even if the moon is not in an exact line with the sun and earth. We 
have seen that the distance of the moon from the earth varies from 



I"k;. 76. An eclipse of the sun. 

222,000 to about 253,000 miles. The moon then is sometimes at her 
greatest distance from the earth at the moment when she passes cen- 
trally over the sun, and sometimes at her least distance, or she may 
be at any intervening distance. If she is near the earth her surface 
just covers that of the sun and we have the total eclipse. If she is 
at the greater distance her disk seems smaller to us on the earth, and 
she does not seem to cover all the sun but leaves a rim of the sun visi- 
ble all around the moon. This is called an annular (ring-shaped) 
eclipse. 

You notice how small the moon's shadow becomes before it 
touches the earth (Figure 76). This spot is never larger than 165 



82 THE moon; its revolutions and phases 

miles in diameter and generally much smaller. It moves across the 
earth in a west to east direction, taking at the most only eight min- 
utes to pass any point on the earth and often passing in two min- 
utes. The true eclipse is visible only to those people living where the 
central shadow falls on the earth, but the partial phases of the eclipse 
may be seen from places aside from the track of the central shadow. 
From the regularity of the movements of the members of the solar 
system, astronomers are able to predict eclipses years in advance. 
On the average, we may observe over the whole earth seventy eclipses 
in eighteen years, twenty-nine of the moon and forty-one of the 
sun. There can never be more than seven eclipses in one year nor 
less than two. 

Effects of the Moon on our Earth. — We learned about the 
force of gravitation possessed by the earth. The moon also possesses 
this power of attracting other bodies to itself, so that it keeps up a 
constant pull on the earth, just as the earth pulls on the moon. Every 
atom on the earth feels this pull of the moon, but all do not obey it. 
The solid land resists the gravitational force of the moon, but the 
drops of water on the earth making up our oceans yield in a certain 
measure to its influence. We are to see later what the effects of this 
moon-pull are. 



questions. — (1) Why is it that only one side of the moon has ever been seen 
from the earth? (2) How are we certain that the moon is a sphere? (3) Can you give 
any reason for doubting whether life exists on the moon? (4) Explain why the moon is 
not always visible from the earth. (5) If you should see the moon to-night from the 
city of Quito would it appear any different from its appearance when viewed from New 
York? (6) Why is it called a dead planet? (7) Give the simple meanings of the follow- 
ing words: phase, eclipse, partial, annular, planet. (8) What two causes produce the 
phases of the moon? (9) In looking at the moon, how can you tell whether it is in the 
first or last quarter phase? (10) When do we see the Harvest moon and the Hunter's 
moon? How did they receive their names? 

EXERCISES. — (1) Write a paragraph describing the surface of the moon as it 
would appear to a traveler from the earth. (2) Make a diagram of the moon revolving 
about the earth. Fill in all the dimensions and distances that you know. (3) Make a 
diagram showing the moon at the first quarter phase. Explain this appearance as seen 
from the earth. (4) Draw and explain the full moon phase. (5) Write a paragraph giv- 
ing an imaginary account of the life of the moon from its beginning to the present. 
(6) Make a diagram to show a partial eclipse of the moon. (See Figure 18.) A total 
eclipse. (7) Make a diagram to show a partial eclipse of the sun. A total eclipse. 



EXERCISES 83 

An annular eclipse. (S) Wliat effect do you imagine the eclipses of the sun had upon the 
minds of people who did not understand their causes? (9) At what phase of the moon 
only can a solar eclipse occur? (10) Why can a lunar eclipse occur only at the full moon 
phase? (11) Draw a picture of the earth as it would appear from the moon. A\'ould it bo 
a light or a dark object? Tell the reason for your answer. 



CHAPTER VII 
THE EARTH'S ATMOSPHERE: DEW, FOG, AND CLOUD 

Our Sea of Air. — We know that the atmosphere is a great 
sea of air forty miles or more in depth, which rests upon the land 
and the water. It completely envelopes the planet, as the earth 
rushes around the sun. The air is a mixture of invisible gases, of 
which oxygen, forming 21% of the whole, is the most important ele- 
ment. Nitrogen forms 78% of it, and then there are argon, carbon 
dioxide, and water vapor present. The nitrogen serves merely to 
dilute the oxygen, since men and animals could not take pure oxygen 
continuously into the lungs. Animals inhale the air, take out much 
of the oxygen, and exhale the residue along with carbon dioxide, 
made up of one part of carbon and two of oxygen. Plants, which 
also breathe air in, have the power of separating these parts of car- 
bon dioxide. They retain the carbon, and breathe out the oxygen. 

The atmosphere then is one of the most important parts of the 
earth. Without it neither man as we know him, nor animals, nor 
plants could exist on the earth. Without it, no winds would blow, 
no fires would burn, no rain would fall, no climatic differences would 
be noticed, and the earth would be a dead planet like the moon. 

The Thermometer. — The amount of heat in the air is meas- 
ured by means of a thermometer (measure of heat). The ordinary 
thermometer is a graduated sealed glass tube terminating in a bulb 
and partly filled with a liquid metal called mercury. Notice the 
point marked 32° in Figure 78. When the atmosphere is cold enough 
to freeze water the particles of mercury draw more closely together 
so that the level stands just at this point. Should the instrument be 
placed in boiling water the mercury would expand and fill the tube 
to the 212° mark. Temperatures in the atmosphere generally vary 
between these two degrees of heat, though temperatures below the 
0° mark on the scale are often recorded. This form of thermometer 

84 



MOISTURE IN THE ATMOSPHERE 



85 



is known as the Fahrenheit, after its inventor, and is the scale gen- 
erally used in the United States and in England. 

Summer temperatures ordinarily range between 76° and 100°. 
The colder temperatures of our winter are below 32° and a temper- 
ature lower than 0° is said to be below 
zero. Near the little town of Verkho- 
yansk in northern Siberia the average 
January temperature is 60° below zero 
( — 60°) and temperatures of more than 
90° below zero have been recorded. This 
region is the coldest known place in 
the world. On the other hand, in 
summer its temperature often is more 
than 95° F. 

Formerly we believed that "the higher 
in the air the lower the temperature." 
From recent experiments we learn that 
the temperature at altitudes above eleven 
miles changes but slightly, and then to 
warmer. The lowest temperature that 
has been recorded high in the air is 85° 
below zero at fifteen miles. The highest 
altitude ever reached by a thermometer 
was 20.3 miles, where the temperature 
registered 48° below zero. 

Moisture in the Atmosphere. — "When the atmosphere a])ove 
the earth is warm, it takes up and holds a great amount of water, 
in the form of vapor. The process by which liquid water becomes 
vapor is called evaporation. When vapor laden air is cooled, it can- 
not hold so much vapor and some of it is changed back into liquid 
water. The process by which a vapor becomes liquid water is called 
condensation. 

We have all seen the moisture in our breath condense, so as to 
form a little cloud, when we are abroad in the cold air in winter. In 
a kitchen, when a kettle of water is heated over a fire, evaporation 
takes place, owing to the heat, and gradually the water disappears 
from the kettle, being changed into vapor. When, however, this 




Fig. 77. A gcysor in oniption. 
Note the condensation of the stream. 



86 



THE EARTHS ATMOSPHERE: DEW, FOG, AND CLOUD 



vapor strikes the cold window panes, it is cooled, becomes liquid, and 
trickles down the pane in little streams. 

The quantity of moisture in the earth's atmosphere (its humidity) 
is measured by an instrument called the hygrometer (measure of 
moisture). Figure 78 shows that the hygrometer consists of two ther- 
mometers, the bulb of one open to the air, while the bulb of the other 

is constantly wet, being covered 
with silk cord or wick immersed 
in water. When you leave the 
water after bathing, you are 
sometimes chilled, because, as 
water evaporates on the skin, 
it causes a loss of heat. In the 
same way, as the water on the 
silk cord evaporates, it will 
cause a loss of heat from the 
mercury and the wet bulb 
thermometer will read lower 
than the dry, pro^nding there 
is a degree of dryness in the 
air. From the lower tempera- 
ture we can ascertain whether 
the air is very dry or contains 
a fair amount of moisture. If 
the air is completely filled with 
water particles, both thermom- 
eters will read alike, as there 
can then be no evaporation. 
Humidity. — The amount of moisture in the atmosphere, or its 
himiidity, is of the greatest importance. Air -without moisture could 
not sustain life, while air too dry causes ill health, catarrh, colds, and 
other diseases of the mucous membrane. Moist air is much warmer 
than warm dry air also, and humidity causes the temperature, as 
shown by the thermometer, to vary as much as 45° from the tem- 
perature as felt by our bodies. If it were not for the moisture in the 
atmosphere, it would be too cold to live in. The reason for this is 
that if the air is dry, the heat goes through it without warming it. 













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Fig. 7S. 
gronieter. 



A Fahrenheit tliermometer. A hy- 
Note the wet and the dry bulb. 



THE FORMATION OF DEW 



If the air is moist, it stops the heat and is warmed ])y it, so tliat liu- 
midity surrounds the earth like a great pall, keeping in its heat. 
If the air lacks moisture, we are 
obliged to secure more heat in order 
to feel comfortable. The dry air 
allows too much heat to escape from 
the body, and this too rapid evapo- 
ration, as we have seen, makes us 
feel cold. 

QUESTIONS. — (1) state why the earth's 
atmosphere is so important to man. (2) 
What determines the height to which an aero- 
plane can rise? (3) Tell how the temperature 
of the air is determined. (4) Tell how the 
humidity of the air is determined. (5) What 
changes might be observed if the earth had 
no atmosphere? (C) What results might be 
observed if the atmosphere lost its moisturr? 
(7) Define evaporation and condensation. (8) 
Tell all the differences between the effects of 
dry and moist air. (9) Explain the gases of 
which the air is made up. (10) Make a dia- 
gram of a thermometer, marking the freezing 
and boiling points. (11) If the temperature 
in New York is 52° F., and the temperature 
in Tomsk is —48° F., what is the difference 

in temperature between the two cities? (12) Why do many people, when crossing the 
Rocky mountains, suffer from difficulty in breathing? (1.'5) A balloon partly filled with 
a light gas was recently sent up in a government experiment. At an altitude of 2.3 miles 
it burst. Explain the reason. 




Fig. 79. Securing cold drinking water 
in the tropics by first permitting evap- 
oration to take place. 



The Formation of Dew. — When any part of the earth's sur- 
face begins to turn away from the sun at night, both the atmosphere 
and the land begin to get cooler. The ground gives off its heat faster 
and cools more rapidly than the air. In this way the lower air touch- 
ing the ground is also cooled, and being unable to hold all its moi.s- 
ture gives up some of its vapor as dew. The temperature at which 
moisture in the air begins to condense is called the dew point. In 
the tropics, where^ there is a great quantity of vapor in the air, the 
amount of dew forming at night is very great. Sometimes the cool- 
ness of the late afternoon will wet the grass with dew even before 



88 THE earth's atmosphere: dew, fog, and cloud 

dark. Grass and leaves are covered with dew sooner than soil be- 
cause they get colder more quickly. Again, because the air is more 
damp, dew is formed more readily near streams or swamps than in 
dr}' places. 

All plants constantly give out moisture from their leaves. Dur- 
ing the daj^ this moisture is evaporated b}' the sun, but at night the 
evaporation is checked and as a result the moisture forms drops of 
water on the leaves. So that dew is the result of two processes, — 
the chilhng of air bj^ the cool ground, and the rising of water from 
plants. Dr}^ air, winds, and clouds are unfavorable to the formation 
of dew: dry air, because it does not contain sufficient moisture to 
give up any of it; winds hinder the formation bj^ carrjang away the 
moisture as soon as it is condensed; while clouds pressing down upon 
the air and the earth prevent the earth from gi^^ing up its heat 
quickly enough to make the air condense bj- becoming colder than 
the earth is. Clear nights are best for the formation of dew. 

Frost and its Effects. — When the temperature of the air is 
below 32°, the freezing point of water, the vapor condensed from 
the cold air takes the form of frost. This is not frozen dew, but vapor 
that has become condensed as a soUd, instead of a liquid. Dew re- 
freshes all plants, and frost always injures them. Sometimes it 
comes so early in the fall that fruit not j^et ripe is destroyed; and 
late spring frosts do great damage to buds. It also causes the autumn 
leaves to change color and to fall. A covering, such as a sheet, will 
prevent the formation of a hght frost by keeping the heat in the 
ground and thus delicate plants may be protected. 

It is very important for farmers and fruit growers to know when 
a frost is expected. They are warned from twent3'-four to thirty- 
six hours in advance by the United States Weather Bureau. The 
value of the orange bloom, vegetables, and strawberries saved in a 
single night in a limited district in Florida bj^ these warnings was 
over $100,000. Fires are often built in orchards of delicate fruits, 
or many lamps are lighted to protect the weak buds from the drop 
in temperature. 

Fog : Its Causes and Effects. — When we breathe into cold 
air, we produce a tiny fog. The tiny drops of water vapor are so light 
that they do not fall to the ground but hang -suspended in the air. 



clouds: their p^ormation and classes 89 

Fog is always formed when damp air is cooled, it often forms at 
night when the air over low, damp ground is chilled to the point that 
it has to give up some of its moisture. It is often caused at sea by 
two currents of air meeting, one cool, the other warm and damp. 

Fogs will form around an iceberg because the air near it is chilled, 
over the surface of a lake, and in damp valleys. On the banks of 
Newfoundland they are common in summer, because the warm air 
from the Gulf Stream strikes the icy winds blowing over the Lab- 
rador current and is condensed (see Figure 122). These and other 
ocean fogs often extend upon the land, as in Maine and Nova Scotia. 

On the Atlantic from 30° to 35° north latitude, fogs are almost 
unknown. But during the month of July the water on the banks 
frequently has a temperature of 45° F., while within a distance of 
less than 300 miles the Gulf Stream has a temperature of 78° F. The 
fog of London is sometimes so dense, due to water collecting on mil- 
lions of dust particles in the air, that traffic is stopped and stores are 
closed. 

Fog is one of the most dreaded dangers of the sea, and careful 
captains reduce speed and sound fog horns to warn other vessels of 
their approach. Many ships have been lost in fogs by collision with 
another ship or, like the ill-fated Titanic, with an iceberg. Figure 
120 shows a freighter which ran aground on shoals during a fog when 
her captain was unable to get his bearings. 

At times the air is filled with small po.rticles of water, which are 
larger than those in a fog and which cause greater dampness. We 
say then that it is *' drizzling " or " misting." The mist is a form of 
condensation midway between fog and rain, and possibly it is made 
of numerous fog particles which have united. Fogs and mists are 
usually seen in the morning when the surface of the earth is cooled. 
When the sun rises and warms the earth and the air, they change to 
invisible vapor. All mists and fogs, being heavier than lower levels 
of the atmosphere, tend to settle down through the air to the earth. 
But when they reach the warmer layers of the atmosphere they are 
evaporated again and disappear. 

Clouds : Their Formation and Classes. — Clouds are also 
formed by the condensation of invisible vapoi". They are composeil 
of particles of moisture, made of fog or mist and, in many cases, of 



90 THE earth's atmosphere: dew, fog, and cloud 




Fig. 80. Cirrus clouds. 




Fig. 81. Cumulus (woolpack) clouds. 



CLOUDS 



91 




Fig. 82. Strato-cumulus clouds. 




Fig. 83. The iiimhiKs or r.'iiii rloud. 



92 THE earth's atmosphere: dew, fog, and cloud 

snow or ice particles. In summer many clouds are formed by the 
rising of warm, damp air. As this rises, it expands and cools and, 
when it can no longer hold all its moisture, fog particles grow, form- 
ing clouds. When damp air is blown against a cold surface, for 
example, a mountain slope as in Figure 164, it has its temperature 
lowered below the dew point, and banner clouds, which extend be- 
yond the peaks, are formed. Finally, when two currents of air 
meet, one being low and warm, the other cold and high, clouds are 
formed. This seems to be the cause of many of the magnificent clouds 
we see in the upper atmosphere. 

Cloud formations are of many different kinds and are known by 
various names. The cirrus cloud (Figure 80) is the highest form 
known, its* elevation often being over six miles. It is formed of many 
feathery forms of fine texture, generally white in color. It is so high 
that the condensation of water forms ice particles, which cause these 
clouds to appear thin and transparent. They drift along rapidly 
and often look like rings around the sun and moon. 

The cumulus {Figure 81) are among the most stately and beau- 
tiful of cloud forms, particularly when lighted by the rays of the set- 
ting sun. They are produced at lower elevations than the cirrus and 
are generally composed of fog particles, rather than ice particles. 
They rise from a flat Base about a mile above the earth and extend 
above this several thousand feet. The rising of air on warm summer 
days is usually the cause of these woolpack clouds, and the broad 
base shows us just where the vapor begins to condense. Frequently 
they develop into thunder heads. They are formed over land more 
readily than over water, and their formation often indicates to the 
navigator the presence of land. 

The strato-cumulus clouds resemble the cumulus, but differ from 
them in being inore massive and banded {Figure 82). They are large 
balls or rolls of dark cloud, which frequently cover the whole sky, 
especially in winter, and give it the appearance of layers or strata. 
Their elevation varies from 500 to 3,000 feet, but sometimes they are 
low enough to touch the earth. 

The nimbus is the rain cloud. It consists of dense masses of dark 
formless clouds with ragged edges, from which generally continuous 
rain or snow is falling. Sometimes the nimbus is torn up into small 



SNOW 



93 



patches, so that these float alonp; much below a great nimbus. Sail- 
ors call these " scud " clouds. 

Many varied forms of cirrus clouds are recognized and various 
names are given to them. Sometimes they are frayed and torn by 
air currents. At other times they occur in bunches, arranged often 
in lines, as if produced by the waves of the air, the groups of clouds 
resembling a choppy sea. The name cirro-cumulus is given when 
these bunches of upper air clouds arc distinct {Figure 85). When 
the sky is speckled with these cloud forms, sailors call it the mackerel 
sky. These formations are a kind of fleecy cloud, — small white 
balls and wisps without shadows, — arranged in groups or rows. 

The alto-cumulus or high cumulus is a dense fleecy cloud, grayish 
balls being grouped in flocks or rows as in Figure 86, frequently so 
close together that their edges meet. 

Snow. — Snowflakes are not frozen raindrops, but when the vapor 
in a cloud is forced to give up its moisture at temperatures below 32°, 
or the freezing point, the vapor crystallizes as it condenses and snow 
results. Figure 84 shows some of the very odd and fantastic forms 
which the snow crystals assume during the change from vapor to 

solid. The same 

storm may produce 
snow on a moun- 
tain range and rain 
down below in the 
vallej^s, owing to 
the difference in 
temperature be- 
tween the t \\' o 

places. The tem- r^^, s^ <^,^^^, ^,^.^^^,3 

perature is 1% 

colder for every three hundred feet of ascent. Oftentimes rain in 
winter is due to the fact that the snow crystals have been melted in 
their downward passage. Damp clinging snows fall before they are 
completely melted into water. Heavy snows cause great damage to 
railroads and force them to maintain a snow-fighting equipment. On 
the great western ranches, thousands of head of liv(^ stock frequently 
perish in the blizzards or northers, as the falls of iieavy snow are called, 




94 THE earth's atmosphere: dew, fog, and cloud 




Fig. 85. Cirro-cumulus clouds. 



Fig. 86. Alto-cumulus clouds. 



HAIL 



95 



before they can be hastened from the ranges to shelter. In large 
cities, traffic is interfered with by snow, and great expense is incurred 
in clearing it from the streets. 

Hail. — Balls of ice, called hailstones, sometimes fall from the 
clouds, generally during thunderstorms or tornadoes. They are usu- 




FiG. 87. A rotary snow plow clearing a railroad track in the west. 

ally oval or rounded in form, and are often made of successive shells 
of clear and clouded ice. We know that the temperature of the air is 
not uniform, but that there are warm and cold currents running 
through the atmosphere. When vapor condenses above 32°, rain is 
formed. When the condensing drops of vapor fall through layers of 
air below the freezing point, the water is frozen. As the stones are 
whirled through different currents of air, they freeze and melt and 
freeze and melt, so that the stone, like an onion, takes on different 
layers or shells. They are sometimes an inch or more in diameter, 
and heavy enough to break windows and do great damage to crops. 

QUESTIONS. — (1) Explain under what conditions dew is formed, (l?) What 
part do clouds play in this process? (3) How is it that no dew forms under a newspaper 
left by chance on a lawn over night? (4) What benefit does the earth derive from dew? 
(5) Explain the difference between dew and frost. (0) How may the effects of frost 



96 THE earth's atmosphere: dew, fog, and cloud 

be offset? (7) State the cause of fogs blowing over New York City. (8) Write as 
manj' effects of fogs as you can think of. (9) Explain the formation and effects of fogs in 
the Atlantic. (10) Write definitions of dew, fog, cloud, frost, mist, snow, and hail. 
(11) Explain the cloud formation seen in Figure 29. (12) Name the various cloud 
forms, and tell how each is produced. (13) Explain the difference between snow and 
haU. (14) Describe the effects of snow and hail on vegetation. (15) How is it that 
snow sometimes falls when the temperature is many degrees above 32° F.? (16) Ac- 
count for the fact that no clouds form above deserts. 



CHAPTER VIII 
VOLCANOES AND EARTHQUAKES — GLACIERS 

The Earth's Heat. — "We have seen that when the earth came off 
from the sun, it was a glowing hot mass of cloud-hke material which 
took the form of a sphere and flattened at the poles as it contracted 
in size. We believe that it has been revolving about the sun for at 
least one hundred million years. During this period it has been los- 
ing heat and cooling, but it is so large that many ages more will be 
required to make it completely cold, like the smaller moon. 

From the fact that the deeper we go into a mine, the higher the 
temperature becomes; that volcanoes cast up molten rock; that 
hot springs bubble up, and that the crust is never at rest, — we believe 
that the interior of our planet is still highly heated. It was formerly 
believed that beneath a thin crust the interior was molten; but now 
it is thought that the centersphere, though very hot, is solid. It is 
solid, because the tremendous weight or pressure of the rocksphere 
upon the centersphere prevents it from melting, since much more 
heat is required to melt a substance under pressure than without pres- 
sure. At a depth of only five miles this pressure is great enough to 
crush rock; so that deep in the interior it is great enough to force all 
particles into a solid mass. The result of this condition is that when- 
ever the tremendous pressure of the rocksphere is lessened or re- 
moved, the interior becomes a hot fluid mass and flows out on the 
surface. 

Springs and Geysers. — The earth consists, then, of a thin, cooled, 
and solid crust surrounding a solid heated interior which is able to 
resume its liquid form. Through this thin crust, the earth water 
often passes in large amounts until, meeting the melted rock of the 
interior, it is heated to the boiling point. When this water flows to 
tiie surface again quietly it is called a hot spring. When it seems to 
collect for a while and gush out at regular intervals and often to great 

97 



98 



VOLCANOES AND EARTHQUAKES GLACIERS 



heights it is called a geyser {Figure 77). Both springs and geysers 
carry mineral deposits which they sometimes deposit at the surface 
in beautiful forms. Certain hot springs in Virginia, Colorado, and 
Arkansas are famous health resorts, because the waters are full of 
dissolved minerals helpful in some diseases. Geysers are found in 
Yellowstone park, New Zealand, and Iceland. 

Volcanoes. — Sometimes the waters of the earth passing down 
through the crust become heated very quickly into steam. This does 
not return at once to the surface but accumulates slowly under the 
strata. Finally the pressure that this pent-up steam exerts becomes 
so great, that the mixture of 




Fig. 88. A volcanic cone in the Philippines 
section of a volcano. 



steam and hot 
water forces its way 
through the crust 
and carries some of 
the melted rock or 
lava with it. This 
lava may escape by 
flowing gently out 
upon the surface 
through fissures 
formed by the growth of mountains, or it may burst out suddenly 
in a volcanic eruption. The place where the explosion occurs 
is generally a spot where the crust has been weakened, so that the 
pressure on the heated interior is at once lessened. When this hap- 
pens, the rock below is reduced to a molten condition again and 
rushes out. It forms about the opening, building a conical peak called 
a volcano. A young volcano is a perfect cone, because each erup- 
tion adds material to it. Sometimes, however, after a period of 



VOLCANOES 



99 




Am. Miu. Nat. Ujst. 



Fig. 90. Mount Pclee belching forth steam and gases. Note the strange spine of lava 
which rose from the crater. 




Fiu. Ul. Mount l'cl('-{' in full eruption. 



Aui. Miu. N>u Ui.l. 



100 



VOLCANOES AND EARTHQUAKES GLACIERS 



quiet, an explosive eruption will blow off the top of the cone and pro- 
duce a saucer-like depression called a crater. At the bottom of this is 
the throat of the volcano. In every eruption vast quantities of steam 
and sulphurous gases belch forth. The expansion of the steam often 
blows the lava to pieces, forming pumice and volcanic ash, which are 

often carried vast 
distances by the 
winds. 

Not all the lava 
that starts toward 
the surface reaches 
it. Sometimes it 
fills up fissures in 
the rocksphere and 
hardens. Later, 
when the surround- 




ing and overly- 
ing rocks have 
been worn away, 
these great lava 
sheets will be 
uncovered. In 
this way the 
Palisades of the 
Hudson were 
formed. Again, 

when a volcano becomes old and eruptions cease, the throat of the 
crater becomes choked with solid volcanic rock, forming a volcanic 
neck or plug. In its idle crater, rain often accumulates, forming a 
crater lake. 

As soon as a volcano appears above the surface, the forces of ero- 



FiG. 92. Crater lake in Oregon, 2000 feet in depth. Fig. 93. A 
volcanic neck. Note how the other material is being worn down 
by erosion. 



THE EFFECTS OF VOLCANOES; MOUNT PELEE AS A TYPE 101 

sion and weathering immediately attack it to wear it down. The 
hases and soft lava forming the cone are worn away more quickly 
than the lava in the throat, and finally the lava plug alone is left 
rising above the surrounding country. 

The Effects of Volcanoes; Mount Pelee as a Type. — Nothing 
in nature is more terrible than a volcanic eruption. The ash, lava, 




Am. Muj. NaU Hill. 



Fig. 94. The ruins of St. Pierre. Mount Pclce is in the background. 

steam, mud flows, gases, lightning, and earth shocks which accom- 
pany outbursts result in terrible destruction of human life, as well as 
animal and plant life. The last great eruption was that of mount 
Pelce on jMartinique in the Caribbean sea, in 1902. The volcano 
had been slumbering since 1851. On Ai)ril 25 warm water was re- 
ported in the old crater, later dust-laden steam issued, and finally on 
May 5 a lake of hot water and mud overflowed the crater and jiourcd 
down the valley. After these warnings the eruption followed ou 



THE DISTRIBUTION OF VOLCANOES 



103 



May 8. A great cloud of steam burst forth bearing gases, ashes, 
dust, and rock high into the air. A break in the crater wall 
opened unfortunately into the valley leading to the city of St. 
Pierre, built on a narrow coastal plain. Along this valley the 
steam with its load of gases and hot rocks rushed like a cloud 
of fire, destroying everything in its path. Other outbursts, in all 
of which the lava seems to 
have been reduced to ash, 
have since followed this first 
one, and a cone 2,000 feet 
high has been built in the old 
crater. Ashes fell at sea 100 
miles from the island. In 
the eruption 30,000 people 
were killed in a few seconds, 
and the city remains only as 
a blackened, desolate waste. 
The Distribution of 
Volcanoes. — Volcanoes vary 
widely in their eruptions. 
Mount Vesuvius in Italy, 
which destroyed Pompeii and 
Herculaneum in 79 a. d., has 
frequent eruptions, some vio- 
lent, some moderate; some of ash, some of lava. Stromboli, between 
Sicily and Vesuvius in the Lipari islands, is alwa^'s active. Origi- 
nally it burst forth at the bottom of the ocean and formed an island. 
Every few minutes the steam in the crater erupts masses of lava and 
often throws molten streams of it down the sides of its cone. Etna, 
on the eastern end of Sicily, pours out lava streams every few years, 
and these make their way to the sea, destroying villages on the way. 
Krakatoa, near Java, in 1883, burst out with a roar heard 150 miles 
away. It produced a water wave noticed in Africa and California. 
The island was destroyed as a place of habitation and 3'), 000 people 
lost their lives through the effects of the eruption. Hawaii, the 
greatest volcanic mountain in the world, rises 30,000 feet above the 
sea floor and 14,000 feet above the sea level. ( )ne of its active vol- 




Am. Miu. Nat, llisU 

Ftg. 96. Looking into the orator of a volcano. 



104 



VOLCANOES AND EARTHQUAKES GLACIERS 



canoes, Mauna Loa, is a crater three miles in diameter. In this the 
lava slowly rises and then freezes since the mountain is so high. No 
^^olent ash eruptions are known in this group. 

We see then that volcanoes are found in all parts of the world. 
There are thousands of cones, but only about 300 are active, and 
these are generally in mountain regions near the sea. Notice how 




Fig. 97. Destruction caused by an earthquake in the West Indies. 



the}' encircle the Pacific ocean {Figure 95). In the western United 
States mount Shasta, mount Hood, and mount Ranier are 
types of extinct or old volcanoes. The Aleutian islands, Iceland, 
the Azores, St. Helena, and the Faroe islands are all volcanic in 
origin. 

Earthquakes. — When mountains are being raised by the folding 
of the crust, the strata of the rocksphere often crack until the whole 
earth shakes from the blow. Volcanic eruptions also produce these 
earth shocks when steam forms in the craters and explodes them. 
Again we may imagine the interior of the earth cooling and shrink- 



THE EFFECTS OF EARTHQUAKES 105 

ing away from the rigid crust. The strata of the crust will break from 
lack of support and drop down to fill up the underlying gaps. All 
these shocks, felt for thousands of miles, arc earthquakes. They 
may be so slight that they can be detected only by instruments called 
seismographs, or they may be so severe as to cause widespread 
destruction. 

The center of an earthquake may be thousands of feet below the 
surface, but the jar from it will pass in all directions, diminishing in 
violence with the distance from the center. The ground may not 
rise and fall more than one inch and yet do great damage. The earth- 
quake, however, is rarely a single shock, but generally a series of jars 
coming in such quick succession as to make one believe the ground 
is shaking. Sometimes 500 or more shocks are felt, an effect which 
is produced by the strata cracking and the rough edges slipping by 
one another. 

"We see from Figure 95 that earthquakes usually occur in the vol- 
canic regions of the earth. Those shocks that precede a volcanic 
eruption are due to the effects of the steam-filled lava breaking the 
rocks in its attempt to escape. The shocks are of frequent occur- 
rence in Japan, Italy, Greece, and South America, though violent 
earthquakes have occurred in other regions. 

• The Effects of Earthquakes. — These shocks rival volcanoes 
in their destructive effects. They change the appearance of the earth's 
crust by creating great cavities which later become lakes; by open- 
ing deep cracks in the land through which pour great masses of steam 
and mud; by causing avalanches which dam streams and form ponds. 
In cities they produce death and devastation by overturning houses. 
In Japan people build their houses very lightly, generally of wood, 
one or two stories high, so that they may withstand ordinary shocks. 
Where cities are built largely of stone, as in San Francisco, great loss 
of iiroperty results. In that city, in 1906, an earthquake lasting only 
sixty seconds destroyed the business section of the city; wliile in 
Italy, at Messina in 1908, 100,000 people were killed as a result of the 
shocks. Earthquakes under the sea produce waves, slight in the 
ocean, but very high when they reach a low coast. In J;ipan and in 
the East Indies tens of thousands of people have been drowned by 
one of them. 



106 



VOLCANOES AND EARTHQUAKES 



GLACIERS 



GLACIERS 

The "Work of Glaciers. — On great mountain ranges, thou- 
sands of feet above sea level, enormous snow fields accumulate year 
after 3^ear, often to a depth of several hundred feet. The pressure of 
the upper layers and the alternate melting and freezing during summer 

davs and nights changes the snow into ice, and gra"vitv begins to draw 




Fig. 100. The Rhone glacier in Switzerland. Note the vallej- it has dug out. 



the whole mass down the mountain valleys in the form of a huge frozen 
river. As this mass moves, pressure and further melting and freezing 
gradually change it to pure, clear ice. Such an ice tongue, filhng up a 
valley, is called a glacier. Some glaciers are fifteen miles long and ma}' 
flow at a speed of about two feet a day. TMien, however, the front of 
the tongue reaches the lower part of the vaUey, the ice melts and a 
river is formed to bear the resulting water to the sea. 

Ever}' glacier, like a river, carries a burden of detritus. It bears 



THE WORK OF GLACIERS 



107 




Fig. 98. Snow field and glacier with lateral moraines in the Alps. 




Fig. 99. Two glaciers joining, showing the formation of a medial moraine. 



108 



VOLCANOES AND EARTHQUAKES 



GLACIERS 



rock fragments fallen from the mountain sides, or ripped from its 
bed. These fragments, slowly dragged along and pressed down by 
the ice, groove and scour the rocks over which they pass. In this 
way again glaciers, like rivers, carry on erosion, deepening and broad- 
ening their valleys. 
The great bands 
of rock fragments 
which form on the 
sides of the ice river 
are called lateral 
(side) moraines. 
When two glaciers 
join, as in Figure 99, 
two lateral moraines 
unite to form a 
medial moraine 
near the middle of 
the glacier. The 
fragments frozen in 
the bottom of a 
glacier are called 
the ground moraine, 
and when a glacier 
has melted entirely 
away this ground 
moraine is left as a 
deposit on the val- 
ley bed. The ad- 
vance of a glacier 
is limited by the 
melting of the ice as 
it reaches warmer levels, and at the end of the glacier all the detritus 
it carries, from fine rock powder to enormous boulders, piles up into 
a terminal (end) moraine. This may become 100 or 200 feet high, if 
the end of a glacier remains in one place for a long time. 

When a glacier is subjected to a heavy strain it cracks, and open- 
ings called crevasses are formed in the ice. The irregular bottoms 




Fig. 101. A crevasse in a glacier. 



THE DISTRIBUTION OF (iLACIERS 109 

of valleys are constantly producing these crevasses, so that the sur- 
face of a glacier is generally broken. 

The Continental Ice Sheets. — It is thought that many thou- 
sand years ago some of the continents were so much more elevated 
than they now are that ice sheets covered them. Northwestern 
Europe and northeastern North America were ice-covered ; a continen- 
tal glacier extended from Canada, east of the Rocky Mountains, east- 
ward and as far south as New Jersey. This ice sheet was thick enough 
to overreach the tops of mountains a mile in height. Evidences of its 
presence are found to-day in great north-and-south glacial scratches 
in rock, and in lake bottoms that were dug out by the ice. In the 
north central states great boulders are found that could have come 
only from Canada. Finally, the presence in these states of valleys 
widened and deepened by the ice, and of the ground moraine or gla- 
cial drift deposited on the surface when the ice melted, is further proof 
of the existence of the ice sheet. 

New York, Pennsylvania, Ohio, and other states along the south- 
ern limit bear many signs, in soil, gravel, smooth rocks, and detritus, 
of the effects of this continental glacier. Thousands of lakes and 
waterfalls within the areas once covered by the glaciers of North 
America and Europe are due to the work of the ice. In New York 
and New England these have proved of great importance in devel- 
oping manufacturing areas. The Great Lakes owe their depth larg(>ly 
to the scouring out of rock basins by the glacial ice, while Niagara 
Falls were a result of the glacial drift forcing the river out of its 
original course. 

It is thought that after many thousand years the land lowered again, 
owing to movements of the crust, and that therefore the continents 
became warmer. Then the ice front slowly melted awa}'', back north- 
wards, leaving its burden behind. This work which it did in carry- 
ing, digging, scratching, and smoothing has led to the ice sheet being 
called a com])iiKMl fi](>, plow, and dump cart of immense size. 

The Distribution of Glaciers. — The work these gnvit ice sheets 
performed in changing the appearance of \hv land can be studied 
to-day in the work now being done l)y the smaller gIaci(M-s occupying 
the ujiper portions of river valleys in Switzerland, Alaska, Greenland, 
and tlie northwestern United States. 



110 



VOLCANOES AND EARTHQUAKES — GLACIERS 



In Alaska the immense Muir glacier is fed by over twenty glacier 
tributaries. Its front is a cliff rising 200 feet above the water 
level and extending 800 feet below it. The great ice stream glides 
slowly down a broad valley and ends in the sea. There are nearly 
2,000 valley glaciers in the Alps, and these serve as one of the 
attractions to tourists. High up in mountain valleys, glaciers are 

found even in Mex- 
ico. Baffin Land, 
Iceland, and Spitz- 
bergen have many 
valley glaciers. 
Greenland, back of 
the fringe of coast 
land, is a great ice 
waste rnore than ten 
times the area of 
New York state. 
This great ice cap 
is sometimes called 
the Greenland gla- 
cier. The interior is often 8,000 feet high, and since snow falls there all 
the year round, there is a movement of ice outward toward the ocean 
in all directions. Antarctica also bears an enormous ice cap whose 
margin is a great ice wall rising several hundred fecL above sea level. 

The Formation of Icebergs. — All glaciers that extend down to 
the sea give off icebergs. The water, getting under the ice cliff, buoys 
it up, causing great masses to break off. Other masses are broken 
off by the water cutting out their under support until they snap off. 
The current of water from the glacier drifts them away from the 
fiords and, melting as they go, they deposit their rocky burdens along 
the sea-bottom. 




Fig. 102. An iceberg in the Atlantic. 



QUESTIONS. — (1) Why do miners work in their shirt sleeves in the coldest 
days in winter? (2) How is it that melted rock issues forth from volcanoes when the 
earth's interior is so solid? (3) Explain the difference between a hot spring and a 
geyser. (4) Why do people spend weeks at the Virginia Hot Springs? (5) In what ways 
may lava rise from the heated interior of the earth? (6) How were the Palisades formed? 
(7) Why does the lava plug of the volcano in Figure 93 rise as a peak above the surround- 
ing country? (8) State the effects of volcanoes upon the earth and upon man. (9) Lo- 



EXERCISES 111 

cate six large volcanoes. Locate the volcanoes in the islands of the sea. (10) What is 
an earfch(iuakc? In what ways may it be produced? Tell the efTects of some great earth- 
quakes upon man. (11) Why do earthquake shocks usually precede a volcanic eruption? 
(12) How docs the distribution of regions that suffer earthquake shocks compare 
with the distribution of volcanoes over the earth? (13) What is the difference between 
a terminal moraine and a ground moraine? (14) In what states should you expect 
to find glacial lakes? (15) Why are so many fences on New England farms made 
of small round stones? (16) Explain the presence of several ledges in Bronx Park, 
smoothed over but bearing long deep scratches. (17) What differences might we 
note if the ice sheet had not extended beyond the St. Lawrence and the Great Lakes? 
(IS) To what parts of the world may tourists go to view glaciers? (19) Explain the 
presence of icebergs off Newfoundland. What effect have they on navigation? (20) Why 
do icebergs always float away from the glaciers? 

EXERCISES. — (1) Make a diagram of a volcano, showing its various parts. 
(2) Write a paragraph explaining the cause of the eruption of mount Pelee. (3) Make 
diagrams showing a young and an extinct volcano. (4) Write a paragraph comparing 
the life history of a river with that of a glacier. (5) Make a diagram of a glacier from 
Figure 9S naming the various parts. (G) On a map of the L^nited States indicate the 
southern limit of the ice sheet. (7) Write a paragraph accounting for the deep valleys 
and rapid rivers of New England and the broad vallej's and slow rivers of our southern 
states. (8) Make diagram of Niagara Falls showing the ledge of hard rock. Explain 
the formation of these falls. Why are they gradually moving back? 



CHAPTER IX 

THE GREAT WIND SYSTEMS 

The Circulation of Air in a Room. — We have often sat near 
a stove or radiator when it was giving off heat and noticed the heat 
waves rising from the hot iron. In the country, lying on the grass 
under a tree at midday, we have seen air currents rising from the hot 
earth. The radiator of an automobile or the hot boiler of a locomo- 
tive has proved to us that when air near a hot body becomes heated, 
it rises from that hot body. 




Fig. 103. The arrows show the circulation of air as produced in the room by 
the radiator. 



In Figure 103 is depicted the movement of the air in a classroom 
due to this fact. As the heated air leaves the radiators, it rises be- 
cause it has expanded in heating and is therefore lighter than the 

112 



THE CAUSE OF WINDS 



113 



surrounding air. The cooler air along the floor hurries in to fill the 
empty space and in doing so it crowds up more of the heated air. 
Meanwhile the heated air continues to rise until it has given off its 
excess heat or till it has ascended to the ceiling. Then, becoming 
cooler, denser, and heavier, it settles again and gradually finds its 
way to the floor, to move again toward the radiators and again fill the 
space left by the warm air that has just risen from the radiators. 

As soon as air is heated, then, it expands, therefore becoming 
lighter, and rising. When air cools, it contracts, grows heavier antl 
descends. Firemen know this fact when, trapped in a room by fire, 
they lie down, with nose close to the floor in order to get cool air into 
the lungs. 

The Cause of Winds. — The vast sea of air lying around the 
earth is acted upon in a mamier similar to the air in tliis room. First, 
the earth in the tor- 
rid zone is heated 
by the direct rays 
of the sun until the 
land there acts like 
a huge radiator and 
causes all the air 
lying above it to 
expand and rise. 
Then the cooler air 
lying to the north 
and south of the 
torrid zone, only moderately heated by the slanting rays of the sun, 
flows in, as Figure 104 shows, and pushes the warm air toward the 
equator and then upward. In this way winds are caused on the 
earth's surface, for wind is merely air moving horizontally. 

Tn Figure 105 we can see what becomes of this air thus driven 
from the equator. We find that it rises several thousand feet and 
then turns to flow toward tlie cold polar regions. To replace it cool 
surface currents flow in from the cooler zones. This cold air stays 
near the earth's surface. As these warm upper currents are continu- 
ally cooling while they travel toward the poles, they will finally de- 
scend to the surface and rejoin the cold currents on their way toward 




Fig. 104. Over the warm regions of the earth the air rises 
and moves toward the cooler regions. 



114 



THE GREAT WIND SYSTEMS 



the equator. Again, the cold currents, as they travel southward along 
the surface, will have their temperature increased and will have to 
rise. You will also notice that near latitude 30° a part of the out- 
flowing currents 
which descend to 
the surface joins the 
cold currents on 
their way to the 
equator, while the 
remainder con- 
tinues toward the 
polar regions to 
take the place there 
of the cold air mov- 
ing toward the 
equator. The rea- 
son for this is that 
much more air is 
required to replace 
the rapidly rising 
currents of the 
equatorial region 
than is required 
near the poles, where the movement of the currents is much slower. 
As a result of this, a point will be reached where the polar-bound 
currents will fall and the equator-bound currents will rise, and no air 
will blow horizontally. 

The Trade Winds. — The air that we found flowing steadily 
toward the torrid zone causes verj^ regular winds called trade winds. 
They begin in the north and south temperate zones and blow toward 
the equator. Therefore they are called the north trades and south 
trades. When the trades become heated they rise to the upper atmos- 
phere and flow back again. They are then called anti-trades (oppo- 
site trades) or return trades {Figure 105). As the air approaches the 
equator, it becomes warmer, and we have learned that warm air is 
better able to absorb moisture. For this reason, the trade-wind area 
on the ocean is noted as a clear-weather belt because these winds ab- 




FiG. 105. The -^and systems of the world. 



116 



THE GREAT WIND SYSTEMS 



sorb all the moisture. The few clouds are high and rapid in motion, 
the sky and sea are a clear blue, and the air is healthful. 

The Equatorial Belt of Calms. — When the warm air is rising 
at the equator and the cold air falling, no air current is blowing hori- 
zontally, so that there is httle or no wind at that part of the earth. 
This region, extending about one hundred miles north and south of 
the equator, is called the belt of calms. To-daj' a steamer chugs along 
as readil}" through calms as through trades; but j'ears ago, when 
sailing vessels carried the greater part of our commerce, captains were 
often forced to wait for weeks in the calms to get enough wind to 
carry them across to the south trades or vice-versa. 

Effects of the Earth's Rotation. — So far we have assumed 
that the trades and anti-trades blow directh^ north and south from 

the equator toward the poles. 
If we consult the wdnd map 
{Figure 107) we see that the 
^ind arrows do not point in 
a north-and-south direction. 
This is explained by the fact 
that the earth does not stand 
still, but, as we have found 
out, the earth is rotating on 
its axis from west to east. 
At the equator the speed of 
this movement is about one 
thousand miles an hour. 
It grows less as we near 
the poles. Gravity tries to 
hold the atmosphere to the 
earth during the rotation 
and tries to carry it along 
at the earth's speed. But the air is the lightest part of the planet; 
and when the earth rotates to the east, the air and all the winds 
with it tend to lag behind, and seem to have a motion in the opposite 
direction. 

The effect of this is, toward the equator where the rotary motion 
is swiftest, to turn trade winds from their straight course. In the 




Fig. 107. The wind belts on the rotating earth. 



THE PREVAILING WESTERLIES 117 

northern hemisphere, the winds are deflected to the right so that they 
blow from the northeast instead of from the north. In the southern 
hemisphere, the winds are deflected toward the left so that they blow 
from the southeast instead of from the south. 

Imagine an axis driven through the sphere in Figure 107, and 
the globe rotated rapidly from west to east. If you should attempt to 
trace with chalk a meridian from the equator to the poles, you would 
produce a series of lines curving to the east as shown in the diagram. 
If you should try to trace a meridian from pole to equator, your at- 
tempts would be lines curving to the west. This aids in showing us 
the effects of our planet's rotation upon the wind systems. 

For the same reason, the anti-trades are turned toward the 
right in the northern hemisphere, where they blow from the south- 
west, and toward the left in the southern hemisphere, where they blow 
from the northwest. The movement of very high clouds and of ash 
erupted from volcanoes proves this fact. On high peaks which rise 
above the level of the trade winds as in the Hawaiian islands, the 
anti-trades may be felt. 

The Horse Latitudes. — We have before noted a region about 
latitude 30° where, both north and south of the equator, much of the 
air of the anti-trades settles to the earth again, as Figure 105 shows. 
Just as in the equatorial belt of calms, so here there can be no steady 
horizontal motion of air, because the movement is downward. This 
is a l)elt of relative calm with irregular, unsteadj^ winds. This region 
formerly was also very trying to navigators, and many vessels in 
voyages from New England to the West Indies were delayed by 
calms. In the early days many of these sailing vessels carrying horses 
were forced to throw them ovorl)oard when the fresh wat(T gave out, 
and this fact gave this belt of calms the name of " horse latitudes." 

The Prevailing "Westerlies. — As we come to the region north and 
south of these horse latitudes, we find that much of tiie air of the anti- 
trade winds settling down to the surface flows on toward tiie poles, 
blowing in an easterly direction. This, we found, was due to the ro- 
tation of the earth. Since the wind blows toward the east, it comes 
from the west and is therefore called a westerly wind. As a result of 
these curnnits, almost all the United States and Canada, northern 
and central Europe, the southern part of South America and the 



118 THE GREAT WIND SYSTEMS 

Southern ocean south of the 40° parallel, receive these westerly winds. 
In this way the westerlies blow throughout the greater part of the 
north and south temperate belts and affect the regions occupied by 
the most important nations of the world. 

Frequent storms in these latitudes interrupt these winds and 
cause them to blow from any direction; but the most constant (pre- 
vailing) point from which they blow in the northern hemisphere is 
the west. In the southern hemisphere, where they have great ex- 
panses of ocean to blow across, and few land elevations to check them, 
these winds are stronger and steadier. For this reason they are here 
known as the Brave West winds. The westerlies, or the Roaring 
Forties, were of the greatest importance to sailors in the days of the 
old clipper ships, but with the coming of steam vessels their influence 
on navigation has been lessened. 

Polar "Winds. — Little is known about the polar winds. They 
originate in the polar regions and blow from the northeast in the 
northern hemisphere and from the southeast in the southern hemis- 
phere. They were generally believed to be stormy but the reports of 
explorers seem to contradict this notion. 

The Wind Belts. — Figure 105 shows us how these belts of 
winds extend around the earth. Notice how the system we have de- 
scribed is repeated around the earth's circumference. Notice the al- 
ternation of equatorial calms, trades, calms, westerlies and polar 
calms. In Figure 106 contrast the regularity of the northern and 
southern westerlies. Water is always more evenly heated by the 
sun than the land is. One region on land may become much 
warmer than another on the other side of a mountain range. In 
the warm area the heated air will rise and winds will blow to fill 
up the empty space in the air. This will change the direction of 
regular winds on land, while on the ocean nothing like this will 
oc€ur. Mountain ranges and high plateaus also turn winds from 
their course. 

Effects of the Earth's Revolution. — We have seen that in 
June the rays of the sun are vertical at the tropic of Cancer. This 
means that not the equator but a belt lying a little north of the equator 
will receive the greatest amount of heat. The warm air will rise and 
the belt of calms will be at that region. So, in our northern summer, 



CLASSIFICATION OF WINDS 119 

the calms shift to a l)olt about 10° north hititude. In December the 
rays are vertical at the tropic of Capricorn and the hottest region 
moves back to a position south of the equator. Since the belt of 
calms moves in this way, all the wind belts of the earth are affected, 
and twice each year we get this slow shift of the winds, northward in 
summer, to the south in winter. 

Classification of Winds. — The trades and anti-trades are called 
constant winds; while the westerlies, which frequently change their 
direction, are called variable winds. Winds always blow toward a 
heated area. During the day you have noticed at the seashore strong 
sea breezes; when the sun sets there is a calm and later the direction 
shifts and we have a land breeze at night. Monsoons are an exchange 
of winds between land and ocean. They are best observed in south- 
ern Asia. From May to October the cool air from the water rushes 
northward upon the heated land to strike the Himalaya mountains. 
During the remainder of the year the land becomes colder than the 
ocean, and the monsoon wind blows from north to south. These 
monsoons (" season ") and the land and sea breezes are called peri- 
odical winds, because they change their direction at the ends of cer- 
tain periods. Irregular winds, caused by many other conditions, are 
verj^ numerous; among them are the winds of thunderstorms and 
tornadoes, and volcanic winds, desert whirlwinds or sand storms, cy- 
clone winds, and waterfall breezes. 

Winds are of the greatest importance to the life of plants, ani- 
mals, and men because they transfer great masses of air from one 
part of the earth to another. Thej^ carry the conditions of heat and 
moisture which exist in the regions from which they come to the 
regions over which they will blow, and as they go on they themselves 
gradually acquire new conditions. Winds blowing over warm waters 
become laden with water vapor, winds from a large land mass are 
dry and may be the cause of deserts in lands to wiiich they l)low. 
Winds moving from a warmer to a colder region l)ring warm, damp 
weather, and winds ])lowing from a colder to a warmer region bring 
cool, dry weather. Most changes of weather are due, as we shall 
find, to changes in the direction of the wind. Some winds are agree- 
able and favorable to life, while some bring sull'ering, destruction 
and death. 



120 THE GEEAT WIND SYSTEMS 

QUESTIONS. — (1) Why do we open the windows at top and bottom to venti- 
late a room? (2) Explain the circulation of air around a lighted lamp. (3) What 
is wind and how is it produced? (4) Name the wind belts from the equator to the 
poles. How is each system produced? (5) In what ways do winds aid man in making 
the earth his home? (6) Describe the effects of irregular wind currents on balloons 
and aeroplanes. (7) What effects would be produced on our wind systems should the 
earth stop rotating? (8) Suppose the axis of the earth had no inclination, how would 
our wind systems vary? (9) TeU whether the westerlies are best developed on land or 
water. (10) Why are winds so regular on the ocean? (11) Explain the causes of trade , 
winds, monsoons, land breezes, and sea breezes. (12) What are the possible effects 
of desert whirlwinds on erosion? (13) Why were the westerlies called the Roaring 
Forties? 

EXERCISES. — (1) Diagram the circulation of air around a candle flame. (2) 
Make a map of the Atlantic, showing the position of trade-wind belts, westerlies, and 
the belt of calms. (3) Make a sketch of the sails of a small boat when moving under a 
stiff breeze, and when caught in a calm. (4) Make diagrams showing the direction 
of land breezes and sea breezes. Tell the effects of these changes on sail-boats. (5) Write 
a paragraph on the effects of the motions of the earth on the wind systems. (6) Make a 
list of the great countries blown over by the westerlies. (7) Make outline maps of 
North America and South America. Show by arrows the direction of the trade winds. 
(8) Change the wind belts in Figure 107 on your own diagrams so as to show their 
positions in the northern summer. 



CHAPTER X 
THE RAINFALL OF THE EARTH 

Rain and its Causes. — We have seen how warm air is able by 
evaporation to absorb a quantity of moisture and to hold it for a time. 
This moisture may be partly condensed when the air cools into tiny 
particles of water and become fog. Fog particles sometimes become 
so large and heavy that they can no longer float, and fall as rain drops. 
Rain, then, is a result of the continued condensation of vapor — the 
union of fog particles, driven together by air currents; or the union 
of particles as they fall through the cloud. The chilling may also 
take place either through the rise of the air into higher and colder 
levels, or through its contact with a colder surface like a mountain 
top, or from its meeting a current of colder air. The rain of the 
world falls either where moist winds blow from the water upon the 
land, from cumulus clouds, or from cyclonic storms. Some of the 
heaviest rainfalls take place on mountains near the sea. 

A gallon of water weighs ten pounds, and if spread out in a layer 
one inch thick will cover an area of two square feet. An inch of rain- 
fall gives one hundred tons of water to the acre, or sixty thousand 
tons to the square mile, yet in the Khasia hills in Bengal, India, the 
rainfall exceeds six hundred inches yearly, the greatest in the world. 
On the other hand less than two inches has fallen in some years in the 
Mohave desert in California. Less than ten inches in any region 
means a desert or tundra. At least twenty inches are necessary for 
forests and for agriculture without irrigation. The lands most favor- 
able for human occupation have from twenty to sixty or eighty inches 
a year. 

Rain and the Winds. — The earth's atmosphere is the great 
carrier of water from ocean to land. The winds sup|)ly tin* motive 
l)<)wer to transport this moisture until it drops again as (l(>w, fog, 
cloud, raiU; hail, or snow. Nature permits nothing to he lost or wasted. 

121 



122 THE RAINFALL OF THE EARTH 

The sun heats the ocean, evaporation takes place, and the warm, moist 
air rises. The winds blow the clouds over the land where they are 
cooled, and the moisture condenses and falls. Then it flows through 
river channels back into the sea again. 

In this way ocean winds cause rain on mountain slopes and pla- 
teaus. The air, being forced to rise in order to pass the elevations, 
expands and cools in the upper regions, and rain generally follows. 
On the other hand when winds descend, the air, being pressed down 
by the weight of the atmosphere above it, is compressed and grows 
warmer. Instead of giving up its moisture it is now able to hold a 
great deal more, so that it seems dry and clear. This descending air 
evaporates water and dries up clouds. Rising air, then, expands and 
cools and brings rain; descending air becomes warmer and brings dry 
weather. 

The Great Rain Belts ; at the Equator. — Here in the belt 
of calms the warm, moisture-filled air of the northeast and the 
southeast trades is continually rising and cooling. In Figure 108, 
note that right around the earth heavy rains fall every day in this 
belt. Rainfall here is the heaviest in the world. The sky is always 
clear in the morning, but as the rays warm the air it rises, filled with 
moisture. So much damp air mounts upward that heavy clouds are 
formed, and these break in heavy rain showers. This lasts all day 
until the sun sets; then the air cools and ceases to rise, the clouds 
disappear, and the stars shine from a clear sky 

In the Trades. — We say that when winds blow over moun- 
tains, the air is raised and condensed so that rainfall results. The 
southeast trades drive moisture-laden winds over Brazil, Madagascar, 
and eastern Australia, and these winds condense to produce heavy 
rainfall in these regions (Figure 108). In South America you notice 
that the western slope of the Andes is dry because these trade winds 
have given up all their moisture on the eastern side. As a result a 
part of Peru is almost a desert. By referring to the physical maps of 
Australia and Madagascar, decide whether this condition is also the 
case on these islands. The northeast trade winds, gathering their 
moisture from the ocean, bring heavy rains. Consult the wind map 
(Figure 106) and note their effect on eastern Asia, the islands north- 
west of Australia, and northern South America. 



124 THE RAINFALL OF THE EARTH 

When a wind blows from a cooler to a warmer region, far from 
being forced to give up its moisture bj^ condensation, it is able to 
evaporate even more moisture and become a drjnng wind. This is 
the case with the northeast trades that blow over northern Africa and 
western Asia. In the first place they have been blowing over land 
instead of over water before reaching these regions and hence can 
have very little moisture; and secondly, since they are becoming 
warmer they take up whatever moisture there is. The Sahara desert 
is a result of this. 

The Prevailing Westerlies. — These winds are good rain car- 
riers. Blowing across the Pacific, they cause abundant rainfall on 
western Xorth America and produce the same effect on northwestern 
Europe. In South America, Chile on the western side has a hea\^ 
rainfall for the same reason that Brazil gets it on the eastern side 
farther north. Here the westerlies carrj^ over moisture from the 
Pacific. It will be noticed that in the belts where the winds blow 
upon the land the rainfall is hea^'^'; while in those places where they 
blow over the land, it is slight. Here the \\-inds blow upon the 
steeply rising land of the Andes. The vapor is condensed b}^ the 
rapid drop in temperature, and the westerlies are drained of their 
moisture. When they blow clown on the ojoposite side, the}^ are dry 
winds, producing deserts. 

These westerlies pass to the south of Africa, but reach New Zea- 
land, the southwest tip of Australia, and the island of Tasmania. 
Figure 108 shows that these regions get ample rainfall. 

The Horse Latitudes. — At the horse latitudes, air is descend- 
ing only and we must expect very little rain. Northern ]\Iexico and 
southern California, southern Spain, Italy, Greece, and the northern 
part of Africa feel the effect of the rainless wind. The middle west- 
ern part of South America, southwestern Africa, and western Aus- 
tralia are likewise afforded little rain. 

Movements of the Rain Belts. — We saw that the effect of the 
earth's revolution on the winds was to shift the wind belts north in 
summer and south in \\inter. This shifting of wind belts causes the 
raiii belts to move also. Figure 106 shows us that many places like 
Central America, Venezuela, and middle Africa are in the belt of 
calms during the summer months and will therefore receive heavy 



TORNADOES 



125 



daily rainfall. But during the winter months, the trade winds will 
sweep them. In this way these places have two seasons: a wet season 
when the region is in the lielt of calms, and a dry season when the 
trade winds blow. 

Storms ; Cyclones. — The prevailing westerlies are also called 
the stormy westerlies because the regions over which they blow are 
subject to frequent storms. A storm is always any condition of 
cloudiness accompanied by rain. Ahnost all of the United States, 
western Europe, the southern part of South America, and the part 
of Australia and the islands nearby (Figure lOS) reached by the west- 
erlies have frequent storms. They are caused by heavier air flowing 
rapidly into a region of light rising air. These incoming air currents 
take on a spiral motion which grows swifter and swifter as they 
approach the center. The inflowing air drives the warm damp air 
upward where it cools and condenses. Clouds and rain follow. The 
stormy area docs not remain in one place but whirls swiftly onward 
across a continent, drawing the air in toward it for hundreds of miles. 
In the United States they always start in the northwest (see Figure 
129), move rapidly eastward, and generally pass over the Great 
Lakes and outward to the Atlantic down the St. Lawrence valley. 
Such a storm is called a cyclone (whirl round). 

Tornadoes. — Some- 
times on very warm days 
the air lying near the sur- 
face of the earth gets very 
hot and full of moisture, 
while the air above the earth 
is heavy and cold. After a 
little the hot air rises sud- 
denly in the form of a huge 
funnel, and the heavy air 
drops down, producing sud- 
den and heavy rainfall. It 
also develops a terrific whirl- 
wind when the surrounding air rushes into the path of the storm. 
These storms often occur in the central and (vistern United States 
in the spring of the year. They are called tornadoes, ami many of 




Fui. 100. PliotoKrai)li of ;i (listaiit tornado. 



126 



THE RAINFALL OF THE EARTH 



them (see Figure 111) have caused an enormous amount of damage, 
smce the wind sometimes reaches a velocity of 200 miles an hour, and 
nothing movable can resist it. 

A waterspout is formed by a tornado at sea drawing up a column 
of water into its funnel instead of taking up air and cloud. The 
larger part of the water, however, is probably formed by the conden- 
sation of the water vapor in 
the air, and not by the uplift 
of water from the sea. 

Thunderstorms are seldom 
cyclonic, but result from the 
rapid rising of currents of warm 
air until hea^y cumulus clouds 
are formed at the top. They 
bring violent gusts of wind and 
a do-umpour of rain, which leave 
the air cool, clear, and bracing. 
Hurricanes. — These are 
destructive cyclonic storms that 
\asit the West Indies in late 
summer and autumn, arriving 
from the southeast. They 
begin in the equatorial calms and increase in expanse until they 
reach a diameter of 100 to 200 miles. On land they destroy 
almost everjiihing — forests, crops, buildings, and people. On the 
sea they are very dangerous to shipping and pile up the water until 
it sweeps over the coast lands, flooding fields and towns. When they 
approach the United States, they usually turn to the northeast and 
die away in the north Atlantic. In September, 1900, the city of Gal- 
veston, Texas, was destroj^ed by a hurricane which passed westward. 
Six thousand lives were lost in this city and the damage to property 
was estimated at more than $30,000,000. Similar storms occur in the 
Indian ocean both north and south of the equator. In these regions 
they are called typhoons. 

Other Causes of Rainfall. — Cyclonic storms pass across Eu- 
rope in the same direction as they pass over our country, changing the 
weather very markedly in a few hours. In the corresponding lati- 




FiG. 110. A waterspout at sea. 



QUESTIONS AND EXERCISES 



127 



tudes of the southern hemisphere also they change temperature, wind, 
and rain. 

In discussing winds we noted land breezes and sea breezes. You 
will be able to see now that sea breezes in summer often bring showers 
of rain, when they come in laden with moisture to strike some ele- 
vated and therefore cool land areas, or to meet some currents of 
cold air. 




Fiii. 111. The effects of a tornado in the middle weijt. 

In studying the monsoons of India, we saw how during six months 
the cool ocean air for hundreds of miles rushes in on the land, and how 
during the winter months the heavy air over the cold land settles 
down as a drying air, and presses outward beneath the warmer air 
which is rising over the ocean. India, then, in the summer has the 
moisture-laden ocean winds carrying the heated air of the continent 
up the steep slopes of the Himalayas and giving her a rainy season. 
In winter she has her dry season, since the land cools more rapitlly 
than the ocean and drives dry air out from the continent. In one 
month of her rainy season, India receives three times as much rain 
as our eastern United States; while during her winter monsoons vege- 
tation withers as in a desert. 

QUESTIONS AND EXERCISES. — (1) What is rain and how is it caused? 
(?) What is the relation of winds to rain? (.3) Why is rain abundant in the belt of 
calms? (4) What rainfall conditions would you note in spending a day on the Amazon? 



128 THE RAINFALL OF THE EARTH 

(5) Explain what is meant by a rainfall of 30 inches. What amount of rainfall is most 
favorable to man? (6) Why is rainfall greatest on the eastern slope of mountains in 
the trade-wind belt and on the western slope in the westerlies? (7) In what directions 
do cyclonic storms move and what is their extent? (8) Why is man interested in 
tornadoes, hurricanes, and thunderstorms? (9) Account for the formation of cyclones. 
(10) Explain why the trade-wind belt contains so many deserts. (11) Make a list of the 
countries in some one continent that lie in the westerlies and which have a heavy rain- 
fall. List those having a light rainfall. (12) Account for the following rainy regions: 
Amazon valley, northern India, rainy season in Cuba, central Africa, Philippine islands, 
southern Chile, the Canal zone. (13) Account for the aridity of central China, south 
Africa, dry season of India, Sahara desert, Argentine pampas. (14) Contrast the 
rainfall of Labrador and Norway. (15) Explain the rainfall of all countries along the 
60° parallel of north latitude; the 20° parallel of south latitude; the 120° meridian of 
east longitude; the 20° meridian of east longitude. (16) Why are the interiors of North 
America and central Eurasia similar as regards rainfall? (17) Why do not the monsoons 
from the Indian and Pacific oceans bring rain to central Asia? (18) Explain the causes 
of the Arabian and the Persian deserts. (19) Indicate the regular rain belts on an out- 
line map of the western hemisphere. Explain the shifting of these belts and its effects. 
(20) What effects do thunderstorms produce in a large city? 

Rainfall of the United States. — In our own country we can 
observe the rainfall conditions of the whole world except those of the 
tropical regions. We have seen the effect of the westerlies bringing 
rain to the western slopes, these winds then losing their moisture 
in passing over the highlands and leaving the middle west with 
little rainfall. Here the country is in an arid and almost a desert 
condition. 

You will observe that the western part is divided into a number 
of north-and -south belts of varying rainfall. Owing to the trend of 
the highlands, the moisture is greatest near the Pacific coast, on the 
windward side of the Coast range, and the still higher Sierras and 
Cascades. Only on the tops of the Wasatch and other high Basin 
mountains does a little rain fall in this otherwise dry region. Again, 
farther east on the still higher and colder Rockies, some more of the 
moisture of the westerlies is condensed. But as we have seen, the 
winds continuing eastward fall on the eastern side of the Rockies and 
here again are drying because they are becoming warmer. Thus they 
render the Great Plains almost arid. 

The great storm belt (see Figure 129) however aids us in under- 
standing why our central and southern states also are not dry and 
desert. Abundant rains fall in this section due to the very irregular 
winds and storms. Practically all the rain falling east of the Rocky 



130 THE RAINFALL OF THE EARTH 

mountains comes as a result of these cyclonic storms tearing across 
the continent. Their moisture is supplied by the gulf of Mexico and 
the Atlantic ocean, and their extent is often so great that one storm 
may be causing rain in Louisiana and Ohio at the same time. 

The rainfall which Figure 112 shows for the Texas coast is the re- 
sult of the inblowing trades of the summer. Florida's rain depends 
upon the nearness of the warm ocean waters. Most of the winds in 
the east are from the land, and of course the rainfall here is less than 
on the western coast. Since w^e pass from warm to cooler areas in 
going from Florida to Maine, the rainfall decreases regularly. On 
the western coast, since the ocean winds blow against mountains, the 
greatest rainfall is in the north and the least in the south. 

Throughout the greater part of the western half of the country 
you notice that the rainfall is very slight, because there are no great 
water bodies to supply the winds with moisture. The same condi- 
tions prevail in central Eurasia. Even in the states just west of the 
Mississippi valley, you notice that the rainfall is light because the 
winds are dry. Whatever winds reach this part from the gulf of Mex- 
ico have lost their moisture on the way. 

REVIEW OF UNITED STATES RAINFALL. — (1) What is the result of 
the absence of lofty mountains in the southern United States? (2) Explain why the 
rainfall of Washington varies from under ten inches to over sixty inches. (3) Explain 
the presence of deserts in Nevada and Arizona. (4) Yv^hich winds are dry in the north- 
eastern United States and which carry vapor? Why? (5) Explain the rainfall in all 
states crossed by the 35° parallel. (6) How does New York City get its rainfall? 
(7) What results might be noticed if the western highlands ran east and west? (8) Can 
you trace any effects of the rainfall differences on the products of the five groups of 
states? (9) Compare the rainfall of Florida with that cf Maine. Account for the dif- 
ference. (10) In what directions do cyclonic storms move and what is their extent? 
How do these affect the rainfall of the United States? 



CHAPTER XI 



THE CAUSES AND EFFECTS OF OCEAN MOVEMENTS 



Waves. — The great expanse of water which forms seven tenths of 
the earth's surface is never at rest. Just as you can produce small 
waves li}^ ])lowing on a saucer of water, so the winds blowing over the 
surface of the ocean produce waves by their friction. The height and 
velocity of these depend on the force of the wind and the depth of 
the basin in which 
they occur. In the 
movement, the 
water particles 
travel forward very 
little, but the 
wave form travels 
through the water 
great distances. If 
A B in Figure 113 
were a rope and 
you should shake 
it violently, you 
would produce a 
wave form passing 

along the rope, though the particles of the cord would move only up 
and down. Water in wave movements acts almost the same as these 
rope particles. 

When a wave approaches shallow water at shore where there is 
not enough water to continue the form, the water advances and the 
wave increases in height and decreases in breadth until at hist the 
top portion falls with a blow on the shore, causing breakers or surf as 
in Figure 1 14- The water which runs down the beach after it has been 
thrown up by the breakers, forms the dangerous undertow of our 
bathing beaches. 

131 




Fig. 113. A diagram of a wave form. 



132 THE CAUSES AND EFFECTS OF OCEAN MOVEMENTS 

In the open sea, with a moderate wind, the height of ordinary 
waves is about six feet, while the distance between two successive 
wave-crests is about fifteen times their height. In storms, waves 
often rise over sixty feet in height and dash along at a speed of sixty 
miles an hour. The wind then mixes much air with the foam and 
spray of the crests and produces whitecaps (Figure 113). 




Fig. 114. The advance of waves on a beach, forming surf. 

Effects of Waves. — Heavy waves, weighing many tons, often 
cause serious damage to ships at sea. Even great liners are often 
forced to change their course to avoid the danger of being capsized 
by them. They dash over the decks, tearing away heavy rails and 
ironwork, smashing lifeboats, and flooding saloons. Many smaller 
vessels, never heard from at sea, have been sunk by them. The carry- 
ing of oil for the purpose of stilling waves in violent gales is now com- 
moui The oil poured over the waves spreads in all directions, and 
the water is calmed because the oily surface offers less resistance to 
the wind. 

In storms, waves do damage on shore also, wrecking pavilions, 
buildings, piers, as well as vessels anchored near-by. The ceaseless 



TIDES 



133 



pound of the surf forms our sand beaches by grinding up pebbles 
and shells. The wave action eats away cliffs and rocks, or cuts them 
into fantastic shapes. In this way, it may often change a coast line 
by cutting it away. Ships are unable to come close to land on such 




Fig. 115. A pier built for the docking of vessels unable to approaeh a regular coast. 

a coast, and it is necessary to extend great piers out into the water 
in order to provide facilities for the discharging of cargoes. 

Tides. — The second principal movement of the ocean water is 
caused bj^ the tides. Twice every day the surface rises and falls in 
a slow, mj'sterious 
movement, that has 
puzzled man for ages. 
The interval between 
high tides is about 
twelve hours and 
twenty-six minutes. 
For six hours the 
water crawls up the 
beaches or mounts 
higher and higher 
around the piles of 
docks and piers until 
it reaches the high 
water mark, and we 
have high tide. Then Fiu. no. a b.a.h at i.>w ii,i-. 

for six hours the 

water ebbs or slowly recedes to low water level, when we ha\'e low 
tide. These movements are called flood tides and ebb tides. 




134 



THE CAUSES AND EFFECTS OF OCEAN MOVEMENTS 




o 



The Causes of Tides. — Hundreds of years ago, it was ob- 
served that the flood and ebb of the tides corresponded with the posi- 
tion and phases of the moon. We have seen that there is the force 
of gravitation always working between the earth and the moon. 
This force will tend to attract to the moon any light part of the earth, 
such as the hydrosphere. The solid land is able to resist the ten- 
dency to move, 
but the liquid 
sea yields to it. 
In this way 
some of the 
water of the 
earth is drawn 
up from the sur- 
face as shown at 
B {Figure 117). 
Since the center 
of the earth, 
upon which the 
moon's pull is 
always concen- 
trated, is 4,000 
miles nearer to 
the planet than 
the water on the 
earth at A, her force will be greater on the center of the earth than 
on this water at A. As a result, when the water at B is attracted, 
the whole globe is next attracted and is lifted up and away from the 
ocean water at A. These two attractions then cause the water to 
rise in two tides as shown, and to become lower at C and D. 

Due to the earth's rotation, this mass of raised water, really sta- 
tionary, seems to move around the earth every twenty-four hours 
from east to west. This diagram shows two flood tides on opposite 
parts of the earth and two ebb tides at right angles to them. In this 
way, each tide will last one quarter of the twenty-four hours, or six 
hours. The duration of the long, low tidal wave is then about twelve 
hours — six hours for the flood and six hours for the ebb. 




■0- 



Fi^.2 



Fig. 117. 1. Flood and ebb tides as produced by the moon. 
2. The formation of tides at the time of new moon. 



SPRING AND NEAP TIDES 



135 



Spring and Neap Tides. — In addition to the gravitational pull 
of the wave on the earth, there is also the attraction of the sun for 
this planet. This power is much greater than that of the moon, and 
a tidal wave is also produced on the earth by the sun. This wave is 
less than one half as high as the moon's, for although the sun's at- 
traction is greater, the sun is so much farther away that its attraction 
is practically 




the same on the 
opposite sides 
of the earth. 
The mere 8,000 
miles of the 
earth's diameter 
makes no ap- 
preciable differ- 
ence. 

Review at 
this point the 
phases of the 
moon. In Fig- 
ure 117 (Fig. 2), 
at the time of 
new moon, we 
find both moon 
and sun uniting 
their force on 
one side of the 

earth in one straight line. A very high tide is produced which is 
called a spring tide because it seems to spring up. In Fig. 3 the 
moon has moved around in its orbit and is drawing on the earth 
along one line while the sun is pulling along another. The lunar, 
or moon tide, is therefore made much less and is called a neap 
(scanty) tide. In Fig. 3, at full moon, the sun's force again unites 
with the attraction of the moon, and again we have a very high spring 
tide. The moon makes its revolution in four weeks; and twice during 
this time we have spring tides at new and full moon, and twice neap 
tides at the first and third quarter. 



Fig. 4 




Fig. 118. 3. The formation of tides at the time of full moon. 
4. The formation of tides at a time half way between new and full 

moon. 



136 



THE CAUSES AND EFFECTS OF OCEAN MOVEMENTS 



Irregular coast lines, different depths of the ocean water, winds, 
channels, and harbor entrances all produce endless varieties of tides, 
so that each place at or near the ocean has its own conditions which 
affect the height and time of its tide. On the open sea, the change is 
between one and two feet, but when the tidal wave strikes the shores 
many variations occur. At New York the spring tide is 5.4 feet above 
low water mark; at Boston, 11.3 feet; at Savannah, 8 feet. At the 
bay of Fundy, a funnel-shaped inlet, the variation between low and 
high tide level is over 50 feet. The Atlantic tide, passing through 
the straits of Gibraltar into the broad Mediterranean, produces no 
effect on it. 

Effect of Tides. — Out on the open ocean, tides are of no im- 
portance. Ships never feel them. But along shore, these currents 




Fig. 119. An ebb tide preventing the docking of an ocean liner. 



are of much importance. Where a channel is narrow and rocky, the 
incoming and outgoing tides change into swift and dangerous 
streams, as in Hell Gate in New York. These are called tidal races. 
Frequently they delay sailing vessels or drive them into dangerous 
positions. Tidal currents along a shore drift vessels out of their 
course and often wreck them. 

When the tide enters the mouth of a river with a strong current, 
the water rises in a high mass which travels upstream very swiftly, 
often wrecking small ships and doing damage along the coast. This 



EFFECT OF TIDES 



137 




rush of water is called a tidal bore. The flood tide then lasts only a 
moment, while the ebb tide follows for about twelve hours. The 
bore is seen at the bay of Fundy, at the mouth of the Severn in Eng- 
land, of the Amazon, and of the Seine. 

Tides and waves constantly change the contour of coast lines by 
either carrying sediment from harbors and river mouths and depos- 
iting it along the 
coast, or by choking 
up harbor entrances 
by depositing sedi- 
ment in them. This 
must be removed by 
the government at 
great cost. Some- 
times they wear 
away the land at 

one place to build Fig. 120. A freighter wrecked on a hidden sand bar. 

it up at another. 

They carry off sediment from the land and produce continental 
shelves like the banks of Newfoundland. Their action, rushing in 

and out of narrow es- 
tuaries, washing out 
the river sediment, 
is often sufficient 
to keep channels deep 
enough for large ves- 
sels. On the other 
hand, they frequently 
deposit the scdimcMit 
outside a harbor, 
producing sand bars 
which are always a 
menace to naviga- 
tion. Sewage dis- 
posal is always easier 

,, , , ^, „ , . for cities near tide- 

in;. 121. I he efleots of a Kiant water wave aceompany- 

iug a storm in the West Indies. water. 





[^^P^P 


^"■. ^ 0: ■ri.i^i ^'^^^^gsl^ 









138 THE CAUSES AND EFFECTS OF OCEAN MOVEMENTS 

QUESTIONS. — (1) How does the wind, blowing over a corn field, make it re- 
semble a water wave? (2) Does water move at all when a wave passes? Explain just 
how it moves. (3) How are breakers produced? What is their effect upon the shore? 
(4) Why is the undertow dangerous? (5) Describe some of the effects of waves on ships 
at sea. (6) Why is oil used in a storm? (7) What effects along shore are produced 
by waves? What are breakwaters? (8) In what other ways does man try to meet the 
effects of wave action? (9) Distinguish between flood and ebb tides. (10) What effect 
would be produced on tides if the earth stopped rotating? (11) "VJ'hat is the effect of 
the sun on tides? (12) Distinguish between neap tides and spring tides. (13) Tell 
about the effects of tides on coast lines, harbors, channels, vessels at sea and near land. 
(1-4) What is the difference between a tidal bore and a tidal race? (15) What difference 
would you note in Figure 116 at high tide? 

EXERCISES. — (1) Make a diagram of four wave forms. Name the parts, and 
with arrows show the movements of the water particles. (2) Make diagrams showing 
the difference between a wave at sea and one nearing a beach. (3) Explain the different 
reasons for building the pier shown in Figure 115 and our piers along the Hudson. 

(4) Make diagrams of the earth, moon, and sun at neap and spring tides. (5) Make 
a list of all the coast formations in Europe which would tend to make tides irregular 
in time and height. (6) Write a paragraph explaining how spring tides and neap tides 
chffer. (7) Make a list of the large tidal estuaries along the coasts of the United States. 

(5) Would a tide run farther up the Hudson of the Mississippi? Why? 

Ocean Currents. — The third principal movement of the ocean 
water is produced by currents. These are practically rivers of warm 
or cold water flowing through the ocean as showoi in Figure 122. They 
are caused by the steady winds blowing over the seas and producing 
not only waves but in addition a slow movement of great masses of 
water underneath the surface. Again, since the rotation of the earth 
affects the winds, it acts also as a cause of the flow of ocean currents. 
A current so slow as to be almost indistinct is called a drift. 

The movements follow a very definite path. The currents in the 
northern oceans move from the east to the west along the equator, 
then to the north and again to the south, turning in the same direc- 
tion as the hands of a clock. The direction of the southern currents 
is opposite to the direction of the hands of a clock. On Figure 122 
trace the effect of the trade winds and the westerlies upon these cur- 
rents. You notice that it is only the continents that deflect them, so 
that winds, coast lines, and other currents determine their direction. 

Warm and Cold Currents. — The water composing the ocean 
currents is warmed in equatorial regions and arrives in higher lati- 
tudes with a higher temperature than the sun is able to maintain at 
that latitude. It therefore is cooled by giving its excess of heat to 



THE GULF STREAM 139 

the water below and the air above, and arrives at the equator again, 
in the eastern part of the oceans, cooler than the equatorial air and 
water. The water and the air at the equator are slightly cooled when 
they give up some of their heat to the cooler current and when they 
aid the sun to warm it again for its westward flow. Thus all cur- 
rents change the temperature of the region they pass through : if they 
come from a warmer region, they raise the temperature; if from a 
colder region, thc}^ lower it. One half of the heat received by the 
whole torrid zone is carried by ocean currents into colder regions. 

-Currents in the Atlantic. — North of the equator, we fitid in 
the Atlantic a west wind drift which, becoming the north equatorial 
drift, due to the effect of the trades, is carried westward toward South 
America. The continent deflects its course, and the rotation of the 
earth sends to the right that part of the current that is permitted to 
go northward. The rotation continues swinging this current to the 
right, so that instead of keeping along the American coast, it swings 
out into the Atlantic toward Europe. Continuing to turn, it breaks 
from the great north Atlantic drift and is again taken in hand by 
the northeast trades. These send it southward, until onc(^ more 
it becomes the north equatorial drift, having made a complete circuit. 
Figure 122 shows us how the equatorial waters of the Atlantic, 
which are drifting westward, are divided at the eastern coast of 
South America. The smaller part is turned to the southwest to 
become the south equatorial drift, and the larger part to tiie north- 
west along the ])order of the continent. 

The Gulf Stream. — Figure 122 also shows how a part of the 
north equatorial drift, following the coast line of Central America, 
flows through the Caribbean sea into the gulf of Mexico. Here, the 
great Gulf Stream is born. This, from its supposed climatic influ- 
ence, the best known of the great currents, derives its name from the 
gulf of Mexico, out of which it flows, between the coast of Florida 
on the one side and Cuba and the Bahama islands on the other, ^^'ith 
a breadth of forty miles in its narrowest portion, it has a velocity at 
times of five miles an hour, pouring along like an innnense torrent. 
At this speed it could flow around Manhattan island in al)out five 
liours. This current flows in a norlhensterly (hrecfion along the 
American coast, gradually witlening and diminishing in velocity, until 



CURRENTS IN THE PACIFIC 141 

it reaches the banks of Newfoundland. Here, about 40° north lati- 
tude, it merges with the north Atlantic drift and approaches the 
coast of Europe. The waters of the stream, from 2,000 to 3,000 feet 
deep, now rise and spread out into a sheet of warm surface water, 
drifting at the rate of a mile or so a day into the Arctic ocean. 

The waters of the Gulf Stream are of a deep indigo blue, with 
boundaries sharply defined against the light green of the seas through 
which it passes in its early course. It abounds with masses of sea- 
weed, torn from the coral rocks when it has its power and velocity; 
and in its warm current may be seen myriads of fish. As it pours out 
of the gulf, it has a warmth of 84° F. in summer, being 4° higher 
than the temperature of the ocean at the equator. Owing to this 
warmth, a bank of fog, rising like a wall, often marks the edge of 
the stream as it meets colder water and air in its northward 
flow. 

The Labrador Current. — We must remember that when any 
quantity of warm water is carried northward, the same amount of 
cold water must find its way to the warm regions. This is why the 
Labrador current flows southward to equalize the distribution of the 
earth's ocean waters. This frigid current comes from the polar re- 
gions, along the coast of North America as far south as the shores of 
Massachusetts. The rotation of the planet swings it to the right so 
that it hugs the coast line. We have seen the effect of these two cur- 
rents, warm and cold, meeting off Nova Scotia and Newfoundland. 

South of the equator in the Atlantic we find drifts similar to those 
of the northern waters, except that the earth's rotation swings them 
alwa3'"s to the left. 

Currents in the Pacific. — Here we find the west wind drift 
shunted Ijy North America to the south, becoming the north equa- 
torial drift, due to the action of the trades. On approaching Asia, 
the drift separates, one part going to the north and one to the south. 
The rotation of the earth swings the north drift to the right, the 
southern part to the left. The west wind drift is taken in charge 
by the westerlies and driven eastward again, thus completing 
the system. 

Near Japan, this northern current is known as the Japan current, 
since it takes up here a vast quantity of heated water and carries 



142 THE CAUSES AND EFFECTS OF OCEAN MOVEMENTS 

it over to the western slope of Canada and the United States. 
In Figure 122 observe the small frigid current that conies through 
Bering strait from the north, corresponding to the Labrador 
current. 

The south Pacific drifts are again the same as those in the north- 
ern hemisphere, except that their direction is toward the left, due 
to the earth's rotation. 

In the Indian ocean, south of the equator, the currents make a 
circuit, which is much like that in the Atlantic and Pacific oceans. 
We have seen how the monsoons of India change their direction twice 
a year. Very soon after the change in winds, the currents north of 
the equator here also change their course. In the summer, when the 
southwest monsoon flows, the currents move from west to east in the 
northern part of the ocean and from east to west in the southern 
part. In the winter, when the wind blows from the northeast, they 
reverse their course to correspond. This is an additional proof of 
the dependence of currents upon winds. 

Around the south pole is the great drift of the Antarctic ocean 
moving constantly eastward, in the same direction as the southern 
part of the eddies of the several oceans. 

Effects of Ocean Currents. — We can see now that the northwest- 
ern coasts of North America and Europe receive the heat and mois- 
ture of air heated by warm drifts of water from the southeast. The 
northeastern coasts of North America and Asia, however, are chilled 
by polar currents that flow southwest from the frigid zone. 

The warm winds from the waters of the Japan current and the 
west wind drift of the Pacific cause the climate of Alaska to be far 
milder than that of Labrador in the same latitude. From California 
north the whole Pacific coast feels their influence in abundant rains, 
mild winters, and cool summers. 

Ocean currents do not themselves warm or cool the land, but the 
air over a warm current is heated by the water and is then blown to 
the land. Without currents in the north Atlantic, the temperature 
over the ocean in the latitude of the British Isles and northward would 
be about 10° or more lower than now. Even without the Gulf Stream, 
the western coast of Europe, since it is in the belt of the ocean wester- 
lies, would have a milder winter climate than the eastern coast of 



WORK OF OCEAN CURRENTS 143 

North America in corresponding latitudes, but the drift of wann 
water into the north Atlantic makes the winter temperature of Europe 
north of latitude 50° considerably warmer than it would be otherwise. 
Hammerfest harbor in Norway, 76° north latitude, is troubled by 
ice about as much as New York harbor, latitude 40°. 

The shifting of the course of the Gulf Stream, due to the action of 
strong winds, sometimes is mentioned as the cause of a mild winter in 
the United States. Winds may force the surface waters out of their 
usual course, but this shifting is always temporary and has little or 
no effect on our winters. 

The chill winds of the Labrador current exert their barren effect 
on the northeastern part of our continent. The waters of the cur- 
rent, reaching the coast of the United States, send out cold winds 
that drive a chill into our seaboard states in winter but lend them a 
pleasantly cool climate in summer. In addition, this current brings 
with it much ice from the Arctic regions. Great icebergs, broken off 
from the Greenland glaciers, are kept frozen in the icy water until 
they come as far south as Nova Scotia. Here they drift into the paths 
followed by trans-Atlantic liners and prove a source of constant 
danger, especially in a fog. 

The same effect as that of the Labrador current is produced off 
the northeastern coast of Asia. The chill winds from the icy waters 
make the Siberian coast l)arren and keep its harbors icebound in 
winter. Notice that Kamchatka and Scotland are in about the same 
latitude. 

Work of Ocean Currents. — Currents have little effect on the 
ocean-bottom, and almost none on coasts, l^ecause in most places they 
touch neither. Where the water is shallow, however, a current may 
scour the bottom, as the Gulf Stream does between Florida and Cuba. 
Since ocean currents eat away but little land, they carry very little 
sediment. Warm currents carry multitudes of plants and animals, 
many of which are very small. These tiny creature.s and their shells 
are scattered far and wide over the bottom of the ocean. The wreck- 
age of ships and driftwood are often carried hnig distances by currents. 
In some places on the seashore driftwood supplied by the ocean cur- 
rents is a valuable source of fuel. In the tropics seeds are often car- 
ried long distances in the same way. 



144 THE CAUSES AND EFFECTS OF OCEAN MOVEMENTS 

QUESTIONS. — (1) Give the three principal movements of the ocean water. 
(2) Name four causes of ocean currents. (3) Name and locate five great ocean drifts. 
(4) Which, in your opinion, is the most important of the currents? Why? (5) Of what 
benefit are ocean currents in frigid and torrid zones? (6) What effects on climate might 
be observed if the Gulf Stream were caused to flow north through Davis strait? (7) On 
the treeless isles northeast of Japan tree trunks and tropical products are often found. 
Account for their presence there. (8) What difference in temperature should you ex- 
pect to find at the eastern and western limits of the tropic of Capricorn in North America? 
(9) When we have a temperature of 40° at New York, it is no colder in the Aleutian 
islands. Account for this. (10) What difference would you expect to find in January 
in the commerce of Vladivostok and Victoria, B. C.? (11) What difference would we 
note if the Japan current ran northwest? (12) In January at latitude 4° north, longi- 
tude 0°, the temperature is the same as at latitude 35° south, longitude 25° east. Ac- 
count for this difference. (13) Why do so many people spend their summers in Maine? 
(14) Account for the fact that the state of Washington has a pleasant climate, while 
Newfoundland is bleak. 

EXERCISES. — (1) Make a chart of the ocean currents as they would move if 
no continents deflected them. (2) On an outline map of the north Atlantic, put in 
the currents, making warm currents red and cold ones blue. (3) Do this for the north 
Pacific. (4) Repeat exercise (2) for the south Atlantic. (5) Repeat for the south Pacific. 
(6) Make two maps of the Indian ocean showing by your arrows the currents in winter 
and summer monsoons. (7) Write a paragraph describing the work of currents in equal- 
izing the temperature of the ocean water. (8) Repeat exercises (2) and (3), shading all 
the places on the oceans where fogs would be likely to form. 



CHAPTER XII 



THE WEATHER OF THE WORLD 



Weather. — Our weather is the result of three things: (1) the 
temperature of the air, (2) the amount of moisture in the air, (3) the 
weight or downward pressure of the air. Differences in tempera- 
ture produce the changes which perhaps we notice most, like winter 
and summer. Weather is fair, stormy, or cloudy as a result of varia- 
tions in the amount of moisture in the air. Differences in downward 
pressure or weight of air cause the horizontal movements over the 
surface of the planet that we call winds. The weather then is the 
total effect in the atmosphere at any given time of heat, moisture, 
pressure, sunshine, clouds, wind, and dust particles. 

Weather Instruments. — We have seen how changes in tem- 
perature may be measured by the thermometer, and changes in the 
amount of moisture by the hygrometer. The anemometer (meas- 
ure of wind) is used to determine the speed 
of the wind. This device has four arms revolv- 
ing horizontally. At the end of each arm is a 
hemispherical cup, generally about three inches 
in diameter. These vanes are connected by a 
steel rod with works which 1)y indicating the 
speed of revolution tell the velocity of the wind. 
This is of great importance in foretelling the 
approach of storms. 

The instrument used to measure the weight of 
the air is called the barometer (weight measurer). 
In its simplest form it consists of a glass tube 
nearly a yard long, sealed at one end. The tube is filled witii 
mercury and supported in a vertical position, as sho^\^l in Figure 1J4- 
At sea level, when the tube is filled, the mercury will fall until the 
scale shows a height of about thirty inches. Since nothing l)ut air 

115 




Fi.:. IL'3. 
iiiouieter. 



An a no- 



146 



THE WEATHER OF THE WORLD 



presses down on the mercury, it must ])e the downward pressure of 
the atmosphere alone that holds it up. Whenever the weight of the 
air is less, the mercurs^ level falls; whenever the air pressure is greater, 
the level rises. 'By measuring the height of the mercury we can esti- 
mate the weight of the atmosphere. This weight at 
sea level is a pressure of 14.7 pounds per square inch. 
The pressure on a grown person would be about 35,000 
pounds. Were it not for the ease with which the air 
under this pressure penetrates the body, we should feel 
slight changes in pressure more than we do. 

The higher up we carrj- a barometer, the lighter the 
pressure of the air in the tube, and the lower the 
mercurv' falls. Figure 126 shows that it falls about 
one inch for everv^ 1,000 feet. It is by noting the 
pressure at different heights and by comparing this 
pressure with that at the seashore at the same time, 
that we can determine the altitude or height of moun- 
tains. At Lead\dlle, Colorado, the barometer registers 
only 20 inches. 

Another form of barometer in wide use is the 
aneroid (without fluid) barometer. In this instrument 
{Figure 125) the pressure of the atmosphere moves a 
delicate surface arranged over a vacuum chamber. 
This force is carried to the index hand mo^-ing over 
a dial which bears a scale similar to that of the mer- 
curial thermometer. 

Weather Conditions. — We have seen how cj^clonic 
storms travel across the United States. We know 
that thej" are certain to come whenever a -^dde area of 
low pressure appears in the west. The low-pressure 
area means that over that area the atmosphere is 
lighter than over the surrounding region. The heaider 
air, from the surrounding countrs', flows toward tliis low-pressure area 
just as water flows from high to low levels. This causes -^dnds to 
blow in from all sides. Such an area of low pressure -vidth its clouds 
and rain is called a cyclonic storm area. 

These storms cause not only rains but also hot and cold waves. 



Fig. 12 4. A 
mercurial barom- 
eter. 



STORM PREDICTIONS 



147 




Fui. IL'O. 

barometer. 



Warm winds blowing toward iho low-pivs.surc areas from the south 
in the winter produce thaws in our central and eastern states; and in 
summer bring hot spells with thunderstorms 
and tornadoes. After a low-pressure area has 
passed eastward and the storm is over (see 
Figure 129), west winds generally blow, pro- 
ducing winter cold snaps. 

Cyclonic storms from the Atlantic pass over 
the British Isles and northwestern Europe. 
Along the northern shores of the Mediter- 
ranean the passage of a cj^clonic area is pre- 
ceded by warm winds from the Sahara. 
Other hot winds probably caused by cyclonic 
storms are the sirocco, a hot dry wind blow- 
ing over southern Italy and Sicily; the solano, a similar wind blow- 
ing over Spain; and the simoom, an intensel}- hot, dry wind from 
the deserts of Nubia and Arabia blowing over the coasts of Arabia, 
Persia, and Syria. In like manner, the cyclone area is followed by 

cold winds in other 
parts of the worKl. 
Among th(>searethe 
northers, cold winds 
l)lowing over Texas 
and the Mexican 
gulf; in Euroi)e, tlie 
mistral, a cold wind 
in the Rhone val- 
ley; and the pam- 
pero, a cold wind 
of the Argentine 
republic. 

Storm Predic- 
tions. — If, then, we can tell the pressure of air over the country 
and locate the low-pressure areas, we shall be able to pretlict such 
storms and weather changes; and by noting their general direction 
and speed, we can warn people of their coming. This is the very 
important work of the barometer and the anemometer. Towanl 




Fic. 126. A diagram showing the 
tude and air pressure. 



rehitiou Ijetwoen alti- 



148 



THE WEATHER OF THE WORLD 



the center of a storm the mercurj^ falls, due to the lightness and 
moisture of the air. The approach of fair weather is foretold bj^ the 
rising of the barometer, due to the dryness and heaviness of the 
air. The anemometer telling the speed of wdnd permits us to work 
out the length of time a storm will take to pass from one region 
to another. The hygrometer measures for us the amount of mois- 
ture in the air at any time. 




Fig. 127. A weather map of the United States. The heavy lines are lines of equal air 
pressure. The figures show the readings of the barometer at these places. 



Barometer Readings. — A rise in the barometer shows that 
heavier air is drifting to a place just before occupied by light air. As 
heavy air has been condensed by cold, a rise therefore indicates a 
cold wind. 

A fall shows that lighter pressures are approaching the station of 
the observer. This means that light air is drifting to a place just 
before occupied by heavj^ air, so that a warm v/ind is coming. A 
falling barometer also indicates a high or low pressure existing near 



WEATHER MAPS 149 

at hand. The fall is then due to the gradual drifting up of the lighter 
air and the drifting away of the heavier air in a whirl. A fall of an 
inch or more is enough to foretell a violent tornado. A stationary 
barometer indicates a continuan'ce of existing conditions. 

The Weather Bureau. — The weather conditions of the United 
States are of the greatest importance to the commercial and agricul- 
tural welfare of the people. Recognizing this fact, the government 
maintains a Weather Bureau at Washington as a special activity of 
the Department of Agriculture. Two hundred branch stations are 
scattered throughout the United States, each equipped with barom- 
eters, thermometers, rain gauges, and snow gauges, anemometers, 
and other instruments. At 8 a. m. and 8 p. m. every day reports on 
temperature and pressure, direction and velocity of winds, condi- 
tion of the sky, and amount of rain or snow are telegraphed from 
these stations to Washington, where they are studied by weather 
experts who trace the paths of storm areas and are thus enabled to 
forecast the weather conditions that may be expected to prevail 
during the following 36 to 48 hours. 

Weather Maps. — When the reports are received weather maps 
are carefully prepared. The solid black lines are traced to run through 
all places which report the same barometric pressures. These lines 
are called isobars (same pressure) and the figures give the barometer 
readings. In this way it is easy to locate the areas of low pressure, 
which are the storm areas. Figure 127 shows the position of a storm 
area over the central states. The storm chart {Figure 120) shows us 
that this is a tropical storm from the gulf of Mexico, and should ad- 
vance north and northeast. Notice the arrows, indicating how the 
winds blow from all sides toward the low-pressure region. Of course 
here the air ascends, expanding and cooling as it rises. This con- 
denses the moisture and sends it down as rain. Farther east on the 
coast is a region of high pressure passing out over the Atlantic. 
Notice the direction of the wind and the surrounding weather con- 
ditions. Farther west is a similar area of high pressure souK^times 
called an anticyclone, while in the northwest there is a small low- 
pressure area which may be the beginning of a cyclonic storm. 

Figure 12S shows the conditions on the following d;iy. Observe 
the movement of the central low-pressure area. Notice how the 



150 



THE WEATHER OF THE WORLD 



western high-pressure area follows it eastward and observe the move- 
ment of the northwestern low-pressure area. You will notice that 
the atmosphere seems to follow a regular wave form, just as we found 
water waves doing. The general movement of '' lows " and " highs " 
in the United States is from west to east, resembling a huge wave, the 
" highs " being the crests and the troughs the " lows." These alter- 




FiG. 128. A weather map for the day following that shown in Figure 127. 
movement of the pressure areas and the storm. 



Note the 



nating " highs " and " lows " have an average easterly movement of 
about 600 to 700 miles a day. 

The United States Storm Chart. — The" storms of the United 
States follow a series of tracks related to each other by well-defined 
laws. The positions of these tracks have been determined by studies 
made in the Weather Bureau. The track that the central point 
of a high area or that the center of a storm follows in passing over 
the country from west to east is laid down on individual charts. 
These are collected on a group chart, and from this the average track 



152 THE WEATHER OF THE WORLD 

pursued can be readil}' described. This chart indicates that there 
are two sets of tracks running westerly and easterly, one set over the 
northwestern l^oundarj-, the Lake region, and the St. Lawrence val- 
ley; the other set over the middle Rocky mountain districts and the 
Gulf states. Each of these is double, with one for the " highs " and 
one for the " lows." The transverse broken lines show the average 
daily movement. 

Let us trace the storms somewhat in detail. A " high " appear- 
ing on the California coast may cross the mountains near Salt Lake, 
and then pass directlj" over the belt of GuK states to the Florida 
coast; or it may move farther northward, cross the Rockj^ mountains 
in the state of Washington, up the Columbia river valley, then turn 
east, and finalty reach the gulf of St. Lawrence. The paths are deter- 
mined by the laws of the general movement of the atmosphere and 
the irregularities of the land surface. This movement of the " highs " 
from the middle Pacific coast to Florida or to the gulf of St. Law- 
rence is confined to the summer half of the year, April to Septem- 
ber inclusive. 

Importance of the Weather Bureau. — These weather maps 
and storm charts are sent out in great numbers and are the means 
of sa\4ng millions of dollars' worth of iDroperty every year by 
giving advance warning of changes. Farmers and gardeners are 
warned against frosts, ship o\^Tiers against hurricanes and storms. 
Sometimes 100,000 telegrams are sent out to all parts of the 
countr3^ to give warnings. By advance notice of one cold wave 
$3,400,000 worth of propertj^ that would, have been destroyed was 
saved. 

Snow and ice warnings are of special interest to those interested 
in the winter wheat crop, to ice dealers, and to the manufacturers of 
rubber goods. Rainfall reports are watched bj^ growers of cotton, 
com, wheat, sugar, and rice. Storm signals are displaj-ed at 300 
points along the coast, and the warnings for a single hurricane are 
known to have detained in port on our Atlantic coast vessels valued 
with their cargoes at over $30,000,000. Flood warnings, often ten 
days in advance, are sent out from 500 river stations and rainfall sta- 
tions so that, especially in the lower Mississippi valle}^, live stock and 
other movable property may be saved. 



EFFECTS OF WEATHER ON MAN 153 

Effects of Weather on Man : in the Cities. — In the cities, 
with notice of an approaching cold wave, greenhouses are closed and 
boilers fired. Preparations are at once made by heating and lighting 
plants, whether gas, electric, steam, or hot water, to meet the in- 
creased demands that will follow. Exposed mains and general plumb- 
ing are protected. Large stockyards drain their mains. Gasoline 
engines are drained. Work in concrete is stopped. Brewing com- 
panies take care of exposed ammonia condensers and water connec- 
tions. Street railway companies arrange for more heat in their cars. 
Natural gas companies turn a larger amount of gas into their lines 
to provide for increased consumption. Merchants curtail advertise- 
ments or direct attention largely to cold-weather articles. Oyster 
dealers lay in a larger stock. Coal dealers supply partial orders to 
all customers needing fuel, instead of full orders to a few, and thus 
please all their patrons. Ice factories reduce their output. The 
dredging of sand and gravel ceases, and iron ore piled up for ship- 
ment is placed in the holds of vessels, to prevent the wet masses 
from freezing solid. Charity organizations prepare to meet increased 
demands for food and fuel, and thus minimize suffering among the 
poor. 

Slight changes in temperature, moisture, and other weather ele- 
ments have been found to affect the quality of products. This is 
true of certain stages in the manufacture of bluing, varnish, oils, 
paper, photographic supplies, chocolate candies, and some acids. 
They also affect the plans of public amusement companies, excur- 
sion enterprises, awning companies, and those engaged in outdoor 
painting. 

Lime, cement, l^rick, drain tile, and sewer pipe material all recjuirc 
protection from rain during the process of manufacture, and cement 
work must be protected from rain for twenty-four to forty-<Mght 
hours after the cement is laid. City departments determine the num- 
ber of teams needed in street sprinkling, railroad companies guard 
against washouts, and irrigation companies control the output of 
water by expected conditions of rainfall. Physicians watch weather 
changes in giving advice to patients suffering with tonsilitis or inflam- 
mation of the throat, nose, or ear, where it is expedient tiiat the suf- 
ferer should keep indoors. 



154 THE WEATHER OF THE WORLD 

Effects of Weather on Man: Transportation. — The railway 
and transportation companies watch weather changes in all their 
shipments. Perishable products are protected against temperature 
extremes by icing or heating, as conditions may require. Often- 
times shipments of perishable goods are hastened when it is found 
possible to carry them to their destination in advance of the expected 
unfavorable temperature conditions. When this cannot be accom- 
plished, goods en route are run into railroad sheds for protection. A 
notice of a cold wave will also often hold up a contemplated ship- 
ment until after the freeze has passed; and, if the cold is protracted, 
the companies will refuse to receive consignments of goods likely to 
be injured by low temperatures. These precautions apply in some 
instances to prospective temperature changes within comparatively 
narrow limits. Bananas, for example, require very careful handling, 
and must be kept at a temperature of 58° to 65° during shipment, as 
a temperature below 55° chills the fruit sufficiently to spoil it, while 
a temperature above 65° inside the car will produce overripening. 

Similar precautions apply to shipments of vegetables, fruits, eggs, 
and other products liable to damage from extremes of temperature. 
On the other hand, most meats are best shipped in cold weather, 
although the use of refrigerator cars prevents loss; and the move- 
ment of live hogs and cattle by freight is avoided, if possible, when a 
hot wave is expected. High temperatures are also hurtful to certain 
other shipments, especially fish and oysters. The shipments of eggs 
kept in storage are largely regulated by temperature changes, the 
announcement of a cold wave being usually followed by brisker ship- 
ments froni western supply districts to the eastern markets, in antici- 
pation of a rise in prices. Temperature changes and cold-wave 
warnings are closely watched by brewers, wine makers, and manu- 
facturers of carbonated beverages. Wine shipments are usually 
withheld until danger from cold is past, as a slight frosting causes 
the acid wine to crystallize. 

Effects of Weather on Man : on the Farm. — In the agri- 
cultural districts, weather changes affect the trucker and fruit grower 
especially in the spring, when the tender vegetables must be pro- 
tected by covering with paper, cloth, or soil, and fruit safeguarded 
by smudging, irrigation, or other methods designed to maintain the 



EFFECTS OF WEATHER ON MAN 155 

temperature above the danger point. In the fall, protection is secured 
in the cranberry regions by flooding the bogs until after the cold 
weather has passed or danger of frost is over. Many crops, such as 
beans and grapes, are saved by being picked in advance of the freeze; 
while tobacco and unmatured corn are cut at once upon advance 
notice of damaging cold weather. Potato digging is suspended and 
the dug potatoes removed from the field, and sugar cane is cut and 
windrowed. The expected duration and severity of freezes govern 
operations in the ice harvest; if the cold is to be prolonged, the ice 
men await the desired thickness, but otherwise the cutting will be 
hastened in order to secure the best possible returns under the cir- 
cumstances. In the spring, changes are watched in the maple sugar 
industry, as the collection and boiling of the sap are more or less 
dependent upon weather conditions. 

The temperature changes are also largely utilized by farmers at 
the time for the killing of hogs, by sheepmen at lambing and shearing 
time, and by stoclanen in general at critical seasons of the year. 

In the raisin-growing districts of California, the crop while drying 
is very liable to injury from rain, and the producers have to protect 
the fruit by stacking and covering the trays. Vegetables dug in dry 
weather are also shipped in better condition than those upon which 
rain has fallen after they have been taken from the ground. Broom 
corn is liable to damage from rain if left in the field. A heavy fall 
of rain upon the alfalfa crop, after cutting, ruins its commercial 
value. 

Effects of Weather on Man: Storms and Floods. — Weather 
changes are watched very closel}^ by men who risk person or prop- 
erty out on the water. Agents of marine insurance companies refrain 
from insuring cargoes after a storm has been predicted. Fishermen 
take steps to protect their boats and nets. Lumbermen make their 
standing booms secure and regulate their log towing. At lake ports, 
vessels load hurriedly if they can get ofT two to five hours in advance 
of offshore winds; if snow is also expected, a start of seven to eight- 
een hours is necessary. Considering the cost of operating a vessel 
whether standing or moving, a day saved from idleness in the harl)()r 
means an appreciable saving in expense. 

Floods affect all river industries, as well as the operations carried 



156 



THE WEATHER OF THE WORLD 



on in the plains subject to inundation. Their approach is followed by 
the removal of cattle from bottom lands and by the saving of such 
crops as can be cut before the high water reaches the threatened dis- 
trict. Fishermen remove their fishing gear from the water so as to 
avoid damage from the driftwood and logs that are brought down 
stream by the rise, and devote their energies to gathering this drift 
for sale. Along the river streets of many cities the basements of 




Fig. 130. The effects of a flood in the Ohio valley. 



warehouses and other buildings are submerged at high water. Wood 
and ties piled along the river banks are made secure by the dealers. 
Coal barges are run aground at a desirable height, and then unloaded 
at leisure after the river falls. Navigation companies arrange for 
the transfer of their offices and landing places from the lower to the 
upper docks. A knowledge of slight rises is often of great value, as 
a small swell frequently permits large movements of water. Lumber- 
men cut much timber in the swamps and along the streams during 
low water, looking to the rises to carry out their logs. During rising 
water, those in charge of locks, dams, and levees are alert to the need 
of strengthening and protecting the property under their care. In 
flood periods, seiners and gill netters determine what class of gear 



EXERCISES , 1 57 

to use to obtain the best results, as different kinds are needed for dif- 
ferent stages of water. Fisliermen in the Columljia river claim that 
the water stage seems to have some effect on the entrance of salmon 
from the ocean, and that a spurt in the run of fish can be predicted 
with a fair degree of accuracy. 

On the other hand, when rivers fall the drop is of considcrahio 
importance to some interests. When the stage falls l)clow a giv(Mi 
height many water-power plants have their water supply cut off, 
and are forced to employ steam power or electricity in order to con- 
tinue their business without interruption. Dock l)uil(ling, pile driv- 
ing, dredging, and repairing are largely done during low water 
stages, previous notice of which enables engineers to arrange for such 
operations. 

QUESTIONS. — (1) What are the elements that make up the weather? (2) How 
does a barometer differ from a thermometer? (3) How does an anemometer diffi^r from 
a hygrometer? (4) What is the use of these instruments in predicting weather elianges? 
"Whieh are the more important? (5) Why does the barometer ^'fall" as it is carried up 
a mountain? (6) If mount Shasta in Cahfornia is 14,380 feet high, how would a 
barometer act during an ascent to the summit? (7) Why is it important to man to bn 
al)lc to predict storms? (8) What is indicated when the barometer falls? When it rises? 
When the mercury remains stationary? (9) Give some results of cyclonic storms in 
Europe, Africa, South America. (10) When the barometer falls in New York wliat 
weather changes may we expect? When it rises? When it falls suddenly at sea? 
(11) Why does an east wind in New York mean overcast skies and rain? (12) What 
is the probable effect of a south wind in New York? (13) Why is it so imimrtaut tc) 
be able to foretell floods? (14) State the connection between floods and rainfall. 
(15) What are some of the effects of weather changes along the coast? (IG) Wliat 
effects of weather changes on the health of j^eople have you noticed? 

EXERCISES. — (1) Writeaparagraphontheworkof the Weather Rureau. (2) From 
the storm cliart (Figure 120) make a list of the states where cyclonic storms occur fre- 
<iuently. Tell about the weather conditions in these states. (3) Write a paragraph 
on the effects of weather changes on farmers. (4) Tell how a weather niai> is made. 
(5) Make an outline map of the United States and insert the Rocky Mountains in an 
east-and-west direction in the southern states. "What effect would this diange liavc on 
our weather condition? (6) On the same map trace the Rocky mountains along the 
Canadian border. What effect' would this change have? (7) Transpose tlie Appa- 
lachian mountains and the Rockies. Tell the effect of this change on our wt-atlirr. 
(S) Write a paragrapii telling hr)W weather changes affect the manufacturtT and tlie 
shipper of poods. (9) Make a diagram showing that high and low pressure areas over 
the United States arc like a wave form. 



CHAPTER XIII 
CLIMATE AND ITS CAUSES 

Weather and Climate. — We have just consiclorod the ntmos- 
pheric conditions, sucli as heat, wind clouds, and rain, that account 
for the weather. But the weather is the result of these conditions at 
any p;iven time only, and we know that the weather changes suddenly, 
especially where the westerlies blow. The climate of a region is more 
stal)lo than the weather and changes very slowly. This means that 
before we say that a region has a hot, rainy climate, we should ob- 
serve and record the weather conditions for as long a period, perhaps, 
as one year. Many days might be temperate and clear, but the greater 
number of days would be hot and rainy. Thus the average of the 
weather in any region is its climate. 

Light Zones and Heat Belts. — The temperature of the earth 
and its atmosphere depends mainly upon the direction of the sun's 
rays. If no other cause interfered, these rays would divide the earth 
into five heat belts or zones, as shown in Figure 131. At the summer 
solstice the perpendicular raj^s would mark the tropic of Canc(T, 
its horizontal raj's the Antarctic circle. At the winter solstice tlu^ 
por]i('n(licul:ir rays would mark the tropic of Capricorn and the hori- 
zontal rays the Arctic circle, and we should have one torrid zone, 
two temperate and two frigid zones. Thes(» zones an^ the result of 
the direction of the sun's ra^^s and are, therefore, only sunlight zones 
and not true heat belts. Tlu\v mark the limit of the variations in the 
slant of the rays as affording light, but they do not mark any exact 
boundaries between liol, temperate, and cold climates. The real heat 
belts you will find marked by very irregular lines which run across 
the map near \\\v. lines separating the light zon(>s. In some parts of 
the temperate zon(>, there is a very hot cHmate, whil(> some parts of the 
frigid zone have a temperate climate. On the highlands oi the torrid 
zone the climate is often temperate or even frigid. 

159 



160 



CLIMATE AND ITS CAUSES 



Isothermal Lines. — In studying weather changes we found that 
places having the same atmospheric pressure at any given time were 
connected on the weather map by lines called isobars. These were 
very helpful in determining areas of low and high pressure. In the 
same way, in studying temperature conditions we draw lines on the 




Fig. 132. An isothermal or temperature chart of the United States for July. 



map through all places having the same average temperature. These 
lines are called isotherms (equal heat), and a map showing them for 
any region is called an isothermal chart. Average temperature is 
ascertained by reading the thermometer at the same time every day 
for a month or a year. 

It is by means of the isothermal lines that we have been able to 
secure the boundaries of the true hot, cold, and temperate belts of 
the earth which, as we have seen, do not correspond with the circles 
and tropics, although they run in a general east-and-west direction. 



CAUSES OF CLIMATE VARIATIONS 101 

In Figure 131, in the Ijroad l:)clt known as tho hot belt, limited by the 
heavy Unes near the tropics, the average temperature of the year is 
more than G8°. You will notice that this belt is broader over the 
land than over the ocean, and extends farther into the northern hem- 
isphere than into the southern. 

The north and south temperate belts border the hot belt, and all 
places within their limits have average temperatures of more than 
50°. You will notice that the north temperate belt is much wider 
than the south temperate belt. It influences more land areas and 
contains the greatest nations of the world. About the poles are the 
north and south cold belts in which the average temperature is always 
less than 50°. Here we find the south cold belt running much nearer 
the equator than does the northern belt. 

Movement of the Heat Belts. — We have read how, at the 
equinoxes, the revolution of the earth brings the sun's rays perpen- 
dicular at the equator, and how at the summer and winter solstices 
the revolution has brought the perpendicular rays respectively to the 
tropic of Cancer or to the tropic of Capricorn. As a result, the heat 
belts also shift up and down the face of the world. In July, when the 
sun is high, the heat belt runs as it is shown in Figure 13S. On the 
other hand, in January, it changes to the position shown in Figure 137. 
The isotherm of 70°, which passes through Maine in July, is found 
in January barely reaching the southern tip of Florida, farther south 
by 18° of latitude. We have already seen how wind and rain belts 
also shift north and south following the sun. 

The Heat Equator. — When we find the point of highest aver- 
age temperature on each meridian and then trace the isotherm con- 
necting these points, we draw the heat equator of the eartii. It crosses 
the northern part of Brazil; extends northwest to about 23° north 
latitude, in the gulf of California; takes a southerly direction below 
the equator; westerly, passing north of New Cluinea; nortlnv(>st uiilil 
it reaches Hindustan; then north to the 23° parallel of north latitude; 
turns south and west across Africa at the 15° parallel of north latitude; 
then southwest across the Atlantic to Brazil. This liru^ is n(>ver tho 
same for two successive days, ])ut swings noi'tli and south with the 
changing position of the sun in the liea\'ens. 

Causes of Climate Variatix)ns: i. Latitude. — As a general 



162 



CLIMATE AND ITS CAUSES 



rule, the farther from the equator, the colder the climate; so that 
latitude is a very important element in determining climate. If land 
and water, winds and currents, did not interfere and the earth's sur- 




FiG. 133. An isothermal chart of the United States for January. Compare the lines 
with those in Figure 132. 



face were perfectly smooth, isotherms would be parallel to the equa- 
tor, the heat belts and light zones would correspond, and latitude 
would be the only factor to consider in determining the climate of a 
region. 

2. Altitude. — One very important cause for the irregular boun- 
daries of these heat belts is altitude, or distance above sea level. 
Records made with barometers and thermometers show that as the 
elevation increases there is gradual decrease in temperature at the 
rate of about 3° F. for every 1,000 feet. There is little warm ground 
to give up heat to the upper-air layers. Because of this, a frigid cli- 
mate is found at the equator at a height of a few miles, and highlands 



DISTANCE FROM THE SEA 



163 



are everywhere cooler tliaii neighburiiig lowlands. As we ascend a 
mountain, then, we encounter lower temperatures, and to find the 
same degree of heat as on a plain, we should have to move toward 
the earth's equator. An elevation of 350 feet is equivalent in its 
effects on temperature to a difference of 60 miles in latitude. When 




Am. Mu«. N»t. HIrt. 



Fig. 134. Subtropical plants in southern France, in the same latitude as Portland, 
Maine. 

an isothermal line crosses a mountain range, it will hend toward the 
equator; when it crosses a plain, it will bend towartl the poles. Trace 
this in the Rocky mountains {Figure 133). 

Quito, situated on the equator, has a temperature like our May. 
while cities in South Dakota have temperatures ranging from 44° 
below zero to 110° above zero. In some of the northwestern states 
the tem[KTature varies 150° during the year. 

3. Distance from the Sea. — We know that tlu' land along the 



164 



CLIMATE AND ITS CAUSES 



seashore soon becomes warm on a summer morning, while out on the 
water the air still remains cool. This is due to the fact that land 
takes in the sun's heat quickly and gives it up or radiates it quickly. 
Water absorbs heat slowly and loses it slowly. Land becomes very 




Fig. 135. The barren regions of Antarctica. 



Am. Mus. Nat. Hist, 



hot in summer and very cold in winter, while the water retains a more 
even temperature throughout the year. The farther a region is from 
the ocean, the more extreme its climate will be. Islands in the oceans 
have cooler summers and warmer winters than places in the same 
latitude on the mainland. In Hawaii the difference between summer 
and winter temperatures is about 7°. Along any seacoast the cli- 
mate is always more even throughout the year than in the interior 
of the continent. 

Thus in Figure 137 we find the average temperature of Kam- 
chatka in January is 10°, while in July it is 55°. In central Siberia, 
far from the ocean, the average in January is about 60° below zero, 
while in July it is about 60° above. Thus the difference between the 
summer and winter inland is about 120°, while in Kamchatka, near 
the ocean, it is about 45°. 



WINDS, RAINFALL, AND CURRENTS 



10 



4. Winds, Rainfall, and Currents. — Winds produoo variations in 
climate, and so tend to nialce isotherni.s curve over the earth's surfa(;e in- 
stead of being straight Hnes. Temperature, humidity, cloudiness, and 
rainfall depend largely 
on the average direction 
from which the wind 
blows. Winds ]:)lowing 
over the land from the 
ocean tend to make the 
climate equal, or equa- 
ble, throughout the 
year. In California, 
Oregon, and Washing- 
ton, the British Isles 
and northwestern Eu- 
rope, the prevailing 
westerlies, influenced 
by the ocean waters 
over which they blow, 
temper the cold of win- 
ter and moderate the 
heat of summer. When, 
however, they blow 
over the land, they 
are very cold in win- 
ter and hot in sum- 
mer. For this reason 
Labrador is Ijarren and 
desolate, receiving the 
cold westerlies from 
the interior of Can- 
ada; while in the same 
latitude in Europe, 
great cities and agri- 
cultural regions (>xist. 

Ocean currents, as we liave seen, nili'd climalr by carrying water 
from one zone to another, becau.se winds i)lo\v over these currents 




Fir,, 
■liiiiati 



130. A part of a mountain range which affecta 

Ijy actiim as a l)arrit'r to wimls. 



WORLD ISOTHERMAL LINES 167 

and have tlieir tomporaturo influenced. Then, blowing upon the lands, 
they influence their climate. Note, again, in Figure 122 the direction 
of the warm north Atlantic drift and then observe its effect on the 
isothermal lines in Figure 137, off Norway and up into the Arctic 
ocean. In Figure 138, off the eastern United States, you note the 
l)end of the lines toward the equator due to the cold Labrador 
current. 

5. Highlands always affect the climate of the neighl^oring r(>- 
gions. The Alps act like a great back door to Italy, southern Spain, 
and France in shutting out the cold north winds and checking the 
southern winds that would carry north the warmth from the Med- 
iterranean waters. In the same way, the equable climate of Cali- 
fornia, Oregon, and Washington is not enjo3^(>d by the states farther 
east on account of the mountain barrier which prevents the moist 
westerlies from influencing the inland parts. The summers then will 
not be tempered by the ocean winds, and the winters will be much 
colder than those along the coast. Again, we have seen how high- 
lands affect the distribution of rainfall. The moisture of the atmos- 
phere condenses on the windward side of mountains, leaving the other 
side more or less arid. 

UNITED STATES ISOTHERMAL CHARTS. — (1) In Fig^wre ^55 note the iso- 
therm of 30°. Why is it so much colder in the interior than on the east coast? (.2) What 
causes account for the warmth of the west coast? (3) Explain the course of this iso- 
therm in crossing the Rockies. (4) Compare with this the effect upon it when crossing 
the Appalachian range. (5) Note the direction of the 40° and 50° lines on the western 
coast. Explain why they run parallel to the coast. (6) Account for the curve of the 20° 
line over the Great Lakes. (7) In Figure 132 trace the course of the 60° line. (S) Find 
the difference in latitude lietvveen the northern and- southern limits of this isotherm. 
(9) Explain why southern California and Maine should have the same temperature in 
July. (10) ,\ccount for the two southerly bends in the isotherm of 70°. (11) Find the 
difference between the summer and winter temperatures on the western coast. Find 
the difference on the eastern coast and compare the two. (12) In general, how do iso- 
t herms bend in crossing the United States? Why? (13) Trace the course of the isotherm 
of S0° and account for its irregularities. (14) Give two reasons for the turning of an iso- 
therm to the north when it crosses a desert region. 

World Isothermal Lines. — In these charts we have lines 
traced all around the world, all places on a given isothermal line have 
the same sunnner or winter temi)erature. We have learned that in 
winter the land is colder than the ocean. This explains why in Fig- 




^ 



Q3 



Q:> 



Co 



QUESTIONS 1G9 

ure 137 the isotherms bend toward the equator in passing over the 
continents. The ocean gives up its summer heat slowly but the land 
very quickly, so that the line must bend toward the warmer equa- 
torial regions to meet the same temperature there. In Figure 13S, in 
the summer, the continental isotherms bend away from the equator 
because the land is now hotter than the ocean water. Notice the iso- 
therms bending toward the equator where they cross the mountain 
ranges. In the southern hemisphere where there is less land to in- 
terfere with climatic conditions, note how regularly the lines of equal 
temperature pass around the earth. Compare the 70° lines in the 
northern and in the southern hemisphere. 

On the ocean, we should expect to see isotherms more regular 
than on land, though affected by warm and cold currents. Note the 
effect of the Japan current and the Gulf Stream in Figure 137. Note 
how the cold Labrador current pushes the lines to the equator while 
the Gulf Stream drives them north. These currents produce a great 
difference in temperature between our northern and southern coasts. 
In the southern hemisphere, note that the isotherms crossing the 
ocean run almost parallel with the circles of latitude. 

The Climate of Different Countries. — Taking into consideration 
the latitude, altitude, distance from the sea, and prevailing winds, 
describe the approximate climate of the following countries: 



1. Brazil 


7. India 


12. 


France 


2. Sweden 


8. Russia 


13. 


Siberia 


3. South Africa 


9. Argentina 


14. 


Spain 


4. Canada 


10. Italy 


15. 


Mexico 


5. Australia 


11. Japan 


16. 


China 


6. Germany 









Verif}^ your results from the rainfall and isothermal charts. 

QUESTIONS. — (1) In what ways docs the climate of New York differ from its 
weather? (2) Explain the difference between isotherms and isobars. (3) What is the 
difference between a heat belt and a light zone? (4) Why is it that the tropics do not 
really separate the heat belts? (5) Name five causes which make irregular the lines sep- 
arating the heat belts. (G) Give reasons why places with the same altitude may have 
different temperatures. With the same latitude. At the same distance from the sea. 
(7) How is an isothermal chart constructed? (S) How do these lines bend in crossing 
mountains? In crossing continents? In crossing small islands? (9) "What causes may 



170 CLIMATE AND ITS CAUSES 

affect their regularity in crossing the ocean? (10) How do mountain ranges affect rain- 
fall and climate? (11) Why do the heat belts move in January and June? (12) How 
does the heat equator differ from the geographical equator? 

EXERCISES. — (1) Note the northern isothermal of 50° in Figure 137. Account 
for its variations around the world. (2) Name the states and countries through which 
the northern isotherm of 40° passes. Explain why these places should have the same 
temperature. (3) Account for the regularity of the 70° northern isotherm. For the 
irregularity of the 70° southern isotherm. (4) Note the circular isotherms in Australia 
and Africa. Explain why they should be found in these places. (5) Explain the isother- 
mal lines on the northern coast of Russia. (6) Why are the isotherms so close together 
off the North American coast and so widely separated off the European coast? (7) In 
Figure 138 explain the 60° isotherms in the northern and southern hemispheres. (8) In 
Figures 137 and 138 can you observe any effects of the winter and summer monsoons 
in India? (9) Why is it that oranges grow in Italy which is in the same latitude as 
New York, while the latter is visited with killing frosts for several months of the year. 
(10) In Figure 137 explain the effect of ocean currents on the isotherms along the west 
coasts of the United States, South America, and Africa. 



CHAPTER XIV 
THE EFFECTS OF CLIMATE ON PLANTS 

The Controlling Power of Climate. — Climate exerts a con- 
trol over all living things on this planet, because it comprises the three 
elements, light, heat, and moisture, upon which their life diepends. 
We are to see now how the factors of climate affect plants, animals, 
and man. 

The Needs of Plants. — Since air is everj^where present over the 




Fuj. 130. A hanilxK) yr<)\c in thr tcinni /.cun 



earth, plant life would exi.st everywhere did not other conditions in- 
terfere. We know that plants cannot live where the tcinpcrature is 

171 



172 



THE EFFECTS OF CLIMATE ON PLANTS 



freezing, because the sap is chilled, so that the nourishment from the 
roots is kept back. Again, plant life is destroyed when subjected to a 
temperature near the boiling point, because such heat causes changes 
which deprive the tissues of their power of action. Sunlight is of 
great importance, because by its aid the green cells change carbon 
dioxide into carbon and oxygen. Notice the bamboo branches in 




Fig. 140. Harvesting sugar cane in Cuba. 

Figure 139 bending to secure their share of the sunlight. The sap is 
the blood of a plant, carrying food and other material to stem and 
leaves. No plant can live without water, for the sap is largely com- 
posed of water. Although soil is not necessary to all plant life, the 
great majority of land plants depend on it for water, food, and an- 
chorage. Plant life, then, depends upon the heat and light of the sun, 
the air and its moisture, and the soil. 

Some low species are able to survive in many climates; but most 
plants are fitted to exist in only one set of surroundings. These thrive 
best where the soil, temperature, and moisture are best suited to fur- 



PLANT LIFE IN THE TORRID ZONE 



173 



nishing them the necessary food. The sugar cane (Figure l-jO) re- 
quires a warm/damp cHmate; cotton needs warmth and sun but can 
stand a lower temperature; corn, though requiring a long warm sum- 
mer, grows much farther north than cotton; and wheat may be raised 
in a climate where corn would die from low temperatures. 

In this way we see there are zones of plant life similar to the belts 




Fig. 141. The dense tangle of the tropical forest. 

of temperature. Each zone has its own characteristic forms of vege- 
tation, and from the polar regions to the equator tiiere is a regular 
gradation of plant life. We do not find the sarhe forms in all the con- 
tinents, because numerous other influences tend to vary them in dif- 
ferent regions. 

Plant Life in the Torrid Zone. — Since plant life depends so 
largely upon heat and moisture, we should expect to find the exten- 
sive and dense forests of the world in the eciuatorial rain belt. Hero 



174 



THE EFFECTS OF CLIMATE ON PLANTS 



grow in wild luxuriance palms, palmettoes, mahogany, teak, rose- 
wood, banana, rubber, and dyewood trees. The daily rains and the 
twelve-hour stretches of sunshine produce the densest kind of jungle 
growth. Along the Amazon and the Kongo, and in Java and the 
neighboring islands, besides the trees, the vines, bushes, and grasses 
cover the ground, and creepers twine around the limbs, the whole 




Fig. 142. In the South American savanna belt. 



forming an almost impenetrable growth. The forests are damp, dark, 
and gloomy. There is no one season of growth, no season when all the 
leaves fall. Blossoms appear and shoots take root at any time. As 
a result of their struggle to reach the air and light, the trees grow 
to a great height, and increase in diameter to support their height. 
They lift up the dense tropical jungle with them, and make an inter- 
lacing canopy above and an intricate tangle below. 

Grasslands or Savannas. — On either side of the tropical for- 
est there are belts in which the temperature is always high, but 
where the seasons are called the dry season and the rainy season. 
Owing to the lack of rain during one season, dense forests are impos- 
sible; but some plants, such as grasses, thrive. These lands, dry 



DESERT VEGETATION 



175 



and barren in tlic dry season, fresli and {j;n'en in the rainy season, 
are known as savannas. The campos of Brazil, the llanos of \'en(»- 
zuela, and the park lands of Africa lying both north and south of 
the equator are examples. In this belt the rainfall ranges from ten 
to forty inches a year, the rainy season lasts only a few weeks, and 

for the greater part 
of the year the vege- 
tation is dried up 
to a brown tint ex- 
cept along the bor- 
ders of streams. 
These are the great 
pasture lands of the 
world, because the 




grasses manage to exist, bridg- 
ing over the dry season by 
means of bulbs and seeds which 
maintain a spark of life. 

Desert Vegetation. — 
North and south of the savanna 
belts are the desert regions of 
the world. We have seen how 
these are the results of the 
westerlies and the trades blow- 
ing constantly over the land, 
or depositing their moisture on 
some mountain barrier. You 
can determine their location, 
generally in the interior of con- 
tinents, by the small amount 

of rainfall (Figure 108). The sunlight, the temperature, and much 
of the desert soil are favora])le to plant life, but water is lacking. 



Fro. 148. Giant cacti of the south 
United States. Fiu. 144. .\ii African 



western 
desert. 



176 



THE EFFECTS OF CLIMATE ON PLANTS 




Fig. 145. A sage brush steppe in South Dakota. 



This is proved by the fact that even in deserts vegetation thrives 
wherever there is fresh water, as along the banks of streams or where 
irrigation has been introduced. 

In desert regions httle vegetation grows except on the higher 
mountains. Where it does exist, it is in the form of coarse grass and 

spiny cacti or simi- 
lar plants, although 
there are some 
shrubs and bushes. 
In the few places 
where water comes 
to the surface, we 
have small green 
spots called oases. 
The rest is made 
up of vast areas in 
which the sand is 
drifted by the wind 
into hills or dunes. Parts of the desert are broad plains, but there 
are also stony plateaus, deep valleys, and mountain ranges. These 
mountains and high plateaus rising from desert lands may have rainfall 
enough for forest growth. On the lower slopes the trees are stunted, 
scrawny, and scattered. Higher up the forest becomes dense. If the 
mountains are high, tree growth may be checked above by 'the cold. 
Vegetation and Altitude. — As the climate varies at different 
altitudes on mountain or plateau, so the plant life changes at various 
heights above sea level in all the belts. The plants of several different 
vegetation regions, like forests, savannas, and deserts, may exist along 
the slopes of any high mountain while the top may be covered with 
ice the year round. Figure 136 shows us the barren top of a peak in 
the Rockies, and below it the timber line, or the line above which trees 
do not grow. Figure 1^5 also shows various kinds of vegetation on 
the side of a mountain. Since it is the amount of available moisture 
that determines the conditions favorable to forest, savanna, or desert, 
the windward side of mountains receiving the moisture-filled ocean 
breezes is usually forested, while' the leeward side may be barren for 
lack of rain. 



PLANT LIFE IN THE TEMPERATE BELTS 



177 



Plant Life in the Temperate Belts. — As we move north or 
south from the savanna and desert belts, we come into the forest 
belts, in the tem- 
perate zones. 
Owing to the mod- 
erate rainfall and 
also to the sever- 
ity of the climate, 
the forest is more 
open than in the 
tropical zone. 
The a b u n d a n t 
rainfall, well dis- 
tributed through- 
out the 3^ear, and 
the supply of sun- 
shine enable the 
temperate belts to 
produce a large 
portion of the food products of the world. 

In the forests near the tropical region the trees are more like those 
of the torrid than of the cool temperate zone. In the cooler parts 




Fig. 14G. A hard-pino forest in tlio tomijcratc hclt. 




-tiiiK 



they are all of hardy varieties, — some evergreen, which have iiccdle- 
like leaves that remain green throughout the winter; others decidu- 



178 THE EFFECTS OF CLIMATE ON PLANTS 

ous, whose leaves first change color when the frost comes, and then 
fall. Among the common evergreens are the spruce, pine, fir, hem- 
lock, and balsam. Deciduous trees include the oak, maple, chestnut, 
elm, and walnut. There are also many fruit trees, like the apple, pear, 
peach, and cherry. In the cleared lands and plains of this belt are 




Fig. 148. The Baraba steppe, a flat plain between the Ob and the Irtish rivers in 
Siberia. 

the great agricultural regions, where corn and wheat are extensively 
raised. 

On the west coast of the United States the damp equable climate 
and absence of strong winds encourage the growth of the ''big trees." 
In southeastern Australia, where exactly the same conditions exist, 
similar great trees are found. 

In some parts of these regions we find great treeless plains called 
prairies or steppes, even though the rainfall is heavy enough for tree 
growth. These steppes, given over to grazing and agriculture, extend 
over a large part of our western states,' and east, west, and north of 
the Caspian sea. They are found in south Africa, eastern Australia, 
and they are the pampas of Argentina. 

Plant Life in the Cold Belt. — As we approach the cold mar- 
gins of the temperate belts, we find that the deciduous trees disap- 
pear and only the evergreens survive in a timber line of low, scraggy 
trees struggling for existence amid unfavorable surroundings. Finally 



SUMMARY OF PLANT ZONES 179 

all trees and bushes are left behind, and in the cold belts we find that 
all plant life is practically dead for two thirds of the year, while the 
temperature is below 32°. In the short summer of a few weeks, in 
June, July, or early August, plants spring up in a thin surface layer of 
soil from which the frost has been melted. This is the tundra region 
north of the Arctic circle. Lichens cling to the rocks and many mosses 
and water-loving plants live in the swampy soil. There are grasses, 
numerous flowering plants, and dwarf willow and birch trees. These 
cling close to the ground, not rising high, because it is important that 
the first snows shall cover and protect them from the cold blasts of 
winter. Three feet beneath this sparse growth of plant life frost is 
ahva3's present in the soil. 




Fig. 149. A view iu Greoulantl .sliowing the bare rock surface with lichens chiigiiig 
to it. 

Summary of Plant Zones. — The three necessary elements of 
climate which all living things demand are light, heat, and moisture. 
In proportion with the supi)ly of tliese elements we have seen that 
the land surfaces of the globe are divided up into a number of belts, 



180 THE EFFECTS OF CLIMATE ON PLANTS 

each marked by some special form of plant life. These are (1) a forest 
belt in the equatorial region, (2) a savanna or open grassland belt 
on either side of the forest belt, (3) an uneven stretch of sand deserts, 
(4) a belt of steppes in the interior of the great continents, (5) a belt 
of cleared plains and woodland, (6) a tiindra belt toward the Arctic 
circle, (7) snow deserts around the poles. 

QUESTIONS. — (1) What are the conditions that produce the equatorial forest 
belt? (2) What conditions of climate produce the savannas? (3) Mention the countries 
north and south of the equator in which we find savannas. (4) Describe the plant life 
of the savannas. (5) Account for the causes of deserts. (6) Describe the vegetation 
found in them. (7) Make a list of the great desert regions of the world. (8) Suppose j'ou 
should climb a peak of the northern Andes, tell what conditions of plant life you would 
observe during the ascent. (9) Describe the observations of plant life j'ou might make 
in crossing the Andes from Brazil into Peru. From Chile into Patagonia. (10) Mention 
the plants of the hot belt that supply food or clotliing. (11) Name the trees of the tem- 
perate belts that you have seen. (12) Describe any changes in the trees you would 
be likely to notice in climbing Pike's Peak. (13) Name the grains and fruits of the temper- 
ate zone upon which man depends largely for food. (14) In what other ways is man de- 
pendent on plant life? (15) Make a list of the tundra regions of the earth. (16) Why is 
the summer so short in these parts? (17) Make a list of some of the plants or trees 
that supply man with drugs. (IS) Do j^ou know of anj' effects produced bj' the cutting 
down of forests? 

EXERCISES. — (1) If the inclination of the earth's axis were 45°, what effects 
would be observed on the plant life of the world? (2) Make a diagram similar to Figure 
107, but instead of winds insert the belts of plant life. (3) Make a list of woods used 
for furniture. State their qualities and the plant belts from which they come. (4) On 
an outline map of the world mark the campos, Uanos, steppes, and prairies. (5) On an 
outline map color aU the desert regions. (6) Describe the different zones of plant life 
you would meet in traveling through South America along the meridian of 60°. (7) The 
meridian of 100° through North America. (8) The meridian of 20° through Africa. 
(9) The meridian of 20° through Europe. (10) Wheat requires an annual rainfall of 
from 20 to 40 inches. Refer to the rainfall map and list the countries in which wheat is 
raised. 



CHAPTER XV 
THE EFFECTS OF CLIMATE ON ANIMALS 

The Control of Climate over Animals. — We have agreed that 
without the hght and the heat of the sun, hfc could not exist on this 
planet. Plants depend on the light and moisture, and in turn all ani- 
mals derive their food directly or indirectly from plant life. They 
need air, water, and heat; and, though unlike plants, they are able 
to move freely from place to place and to maintain a certain temper- 
ature in their bodies, still climate exerts a powerful control over them, 
and restricts them to certain well-defined areas. Their distribution 
over the earth is, of course, closely related to the distribution of plant 
life. The flesh-eating animals, also, depend upon plants. ])ecause the 
weaker animals that furnish them food derive their living from grass 
and other vegetation. 

Their Adaptation to Surroimdings. — Like plants, animals are 
adapted or changed in many ways to meet the climatic and other 
conditions of their surroundings. Some, to survive freezing tempera- 
tures, are protected with a covering of fur, feather, or fat. IVIost water 
animals and many land animals are cold-blooded and can change 
their temperature with their surroundings. Some of these require 
so little air that they obtain all they need from the water; while the 
warm-blooded animals take out oxygen from the air they inhale, their 
warmth being due to slow combustion in their l)odies caused by the 
oxj^gen. The bodies of animals are widely adapted to their mode of 
life. Wings are developed for flying; fins, scales, and boat-siiapcd 
bodies for swimming; long legs for running; and arms, claws, and 
tails for climl)ing. In the polar regions, animals are white, like the 
bear and the ptarmigan; in the desert regions they become a grayisii 
brown; in the steppes and prairies they are a lighter brown; in the 
tropical forests many of the birds and insects are green, in imitation 

181 



182 THE EFFECTS OF CLIMATE ON ANIMALS 

of the foliage. The effect of this variation in color is to render them 
less easily seen by their enemies. 

The Distribution of Animals. — The spread of animals over the 
earth is interfered with by the same climatic barriers as in the case 
of plants. Rivers, oceans, mountain ranges, deserts, and tropical 
forests are the great barriers that exclude animals from different 
regions. Sometimes animals pass these barriers; they may bo 
carried from one place to another, like birds, by wind or sea; by 
ocean or river currents, like animals on floating tree-trunks; or they 
may be accidentally or purposely carried by man from one region 
to another. In this way, the rabbit was introduced into Australia, 
the brown Norway rat into this country, and cattle and horses into 
Argentina. 

Animals accustomed to a warm climate cannot cross to the other 
side of a cold, rugged mountain range; the tropical forest is a barrier 
to the desert animal; and the desert cannot be crossed by one that 
needs water every day. Domestic cattle would soon perish in Green- 
land, where the musk ox seems not to suffer at temperatures 80° 
below zero. Polar bears brought to temperate regions must be con- 
stantly supplied with ice. Owing to its separation from the main- 
land, Madagascar possesses animals entirely distinct from those of 
the neighboring coasts of Africa. Finally, there are the two great 
invisible barriers of heat and food supply. The climatic conditions 
of the north and south temperate belts are about the same, yet we can- 
not imagine their different animals intermingling, on account of the 
climatic barrier of the intervening hot belt. 

The Regions of Animal Life. — In considering the distribution 
of animals as affected by climatic concUtions, we divide the earth into 
five great regions: the North American region; the Eurasian region, 
including Europe, northern Asia, and northern Africa; the South 
American region; the African region, embracing that part of the con- 
tinent south of the Sahara; the Oriental region, including India and 
southeastern Asia; and the Australian region. 

The isothermal lines which indicate the conditions of heat, mois- 
ture, and vegetation cannot be taken as the actual boundaries of ani- 
mal life, as they do not take into account the changes produced in the 
species of animals by the various natural barriers we have spoken of. 



ANIMALS OF NORTH AMERICAN REGION 



183 




I'li:. l.")(). Some aniiiKils of tlir Ndrili Aiiii'ricMii ri !M"m 



184 THE EFFECTS OF CLIMATE ON ANIMALS 

These lines could be used only if the earth were all land surface with- 
out any irregularities. 

1. The North American Region. — No animals live in the 
interior of Greenland, but in and near the Arctic ocean there is 
much life. The polar bear, walrus, and seal live on the ice; the 
musk ox, caribou, hare, and fox live on the bare tundras, while the 
birds, like the wild geese and ptarmigans, migrate to the south in 
winter in search of food. No reptiles live here, because of the great 
cold. 

In the temperate belt animal life is more varied. The wolf, fox, 
grizzly and black bear, lynx, cougar, moose, elk, and deer are found 
here. The Rocky mountain sheep and goat, antelope, opossum, 
beaver, and otter are among the characteristic animals. Many ro- 
dents are found, such as prairie dogs, rats, squirrels, and rabbits. 
The eagle, owl, and wild turkey are among the large birds; and there 
are hundreds of varieties of small birds, many of which are helpful to 
man. They live on insects that are harmful to plant life, and they 
eat the grubs which develop into destructive insects if not destroyed. 
Practically all of these birds are migratory; and while naturalists 
do not agree fully as to the reasons for their migrations, we do know 
that they travel in search of warmth and food, and climatic conditions 
that tend to afford protection in raising their young. Among these 
are the woodpeckers, the thrushes, the sparrows, the finches, the 
warblers, the blackbirds, and the orioles; the hawks and the vul- 
tures; game birds, such as the partridge, the quail, canvas-back and 
redhead ducks; as well as other aquatic birds, such as the gulls, the 
tern, and the heron. 

2. The Eurasian Region. — The animal life in the Arctic zone 
of this region is the same as that found in the cold belt of North 
America. In the temperate belt, which is of enormous extent in this 
region, reaching through nearly one half of the earth's circumference, 
there is a wide range permitted to its animal life because of the ab- 
sence of any north and south barriers. In addition to most of the 
animals of the North American regions, there are the European bear, 
reindeer, hare, ibex, and the chamois of the Alps. The dromedary, 
camel, yak, and wild horse are found in the eastern part. In general, 
this region is the home of the hoofed grass-eaters. Beasts of prey 



ANIMALS OF EURASIAN REGION 



185 




Il'j. l.Jl. S.jiu.- aiiiiii.iN 'ii til' I 



186 THE EFFECTS OF CLIMATE ON ANIMALS 

are few and inferior in size. Man has killed off the flesh-eaters and 
bred the grass-eaters. 

3. The South American Region. — Here the great forest, open 
grassy plains, great mountain region, and tropical areas support 
a wide variety of animal life. The chinchilla, alpaca, llama, and 
vicuna, all related to the camel family, inhabit the slopes. The mon- 
key, the armor-covered armadillo, the sloth, the ant-eater, and the 
tapir are found. The jaguar is the only dangerous wild animal. The 
rhea is called the American ostrich; the huge Andean condor lives 
there, as well as humming birds, macaws, toucans, parrots, and 
umbrella birds. The boa constrictor, anaconda, alligator, and lizard 
are among the reptiles. Insect life is exceedingly varied. 

4. The African Region. — Here we have a vast desert tract in 
the north, an equatorial forest region, and then belts of open savanna 
and prairie land. The region is remarkable for the development of 
its flesh-eating and its hoofed animals. The former are represented 
in the lion, leopard, panther, hyena, jackal, and wolf. Among the 
grass-eating animals are the long-necked giraffe, the buffalo, and the 
many varieties of antelope like the gazelle, the hartbeest, the horned 
gnu, the eland, and the springbok. The striped zebra, the smaller 
quaggas, and the wild ass are among the horse-like animals. The 
man-like gorilla, the chimpanzee, and the monkey, the five-toed ele- 
phant, the hippopotamus (river horse), and the rhinoceros (horned 
nose), dwell here. Among the birds are the ostrich, the hornbill, the 
secretary bird, the parrot, and the plantain-eater. The reptiles include 
the puff-adder, the boa, the python, the lizard, the crocodile, and the 
chameleon. No other region rivals this for the ferocity, strength, 
and size of its animals. Madagascar, owing to the water barrier be- 
tween it and the mainland, possesses a different animal life. The 
lemur, a monkey-like, night-prowling animal, is characteristic of it. 

5. The Oriental Region. — The animal life here resembles that 
of Africa, since the physical conditions are similar. A luxuriant 
tropical forest covers much of the country, and open pasture lands 
are found in some of the mature river valleys. Here are found the 
lion, cheetah, tiger, rhinoceros, leopard, and the Indian or three-toed 
elephant. The long-armed gibbon and the orang-outang are found 
in the East Indies. 



ANIMALS OF SOUTH AMERICAN REGION 



187 




I"i(i. 152. Soino :iiiiiii:il.s of tlic South AiiuTiiim ri'iiinn. 



188 



THE EFFECTS OF CLIMATE ON ANIMALS 




-■"■ GIRAFFE 



Fig. 153. Some animals of the African region. 



ANIMALS OF ORIENTAL REGION 



189 




Fii;. 154. Sonio animals of llic Oriontal roKioii. 



190 THE EFFECTS OF CLIMATE ON ANIMALS 

The Oriental region was the original home of most of our common 
domestic animals. The zebu or water buffalo, the elephant, and the 
zebra are here trained to do useful work. The chicken is a native of 
this region. Among other birds are the bee-eater, bird of paradise, 
parrot, pheasant, and tailor bird. The giant python, the cobra, 
viper, lizard, and the crocodile of the Ganges delta, are among the 
reptiles. Sumatra, Borneo, and the Philippines are part of the Ori- 
ental region, and only a narrow channel of deep water separates this 
region from one whose animal life is widely different. 

6. The Australian Region. — The surface and rainfall condi- 
tions of this island help us to understand its strange animal life. 
It is a plateau so poorly watered that much of the west and center 
is practically a desert. On the east and southeast the land is well 
watered and is covered with forests. 

In Australia there are animals entirely different from any we have 
studied. Among the birds are the emu and the cassowary, which 
are without wings but have developed long powerful legs; also par- 
rots, the laughing jackass, lyre birds, and the cockatoos. There are 
various kinds of kangaroos, some living on insects, some on plants, 
and some on flesh, as their surroundings demand. They vary in size 
from the giant kangaroo to the very small kangaroo rat, and they 
are called marsupials (little pouch) because they carry their helpless 
young in a fold of skin on the under side of the body. Their long 
muscular tail aids them to hop on their hind legs. The duck- 
billed platypus or mole lays eggs, although it is classed among the 
mammals. 

On account of the sinking of the land and the water barrier thus 
developed, the fiercer animals of southern Asia and the East Indies 
have not been able to reach Australia, so that the defenceless animals 
of this continent, which really belong to a past age of the planet's 
history, still survive. The Australian region includes also Tasmania, 
New Zealand, and the neighboring islands, on all of which the ani- 
mal life is about the same. 

Domestic Animals. — Man domesticates animals by changing 
them from their natural wild state to a condition where they can be 
trained to give useful service. Climatic control often prevents the 
spread of domesticated animals over the earth, so that, for example, 



ANIMALS OF AUSTRALIAN REGION 



191 




I'lu. loo. Soiiu" aiiiiiu.ls of the Aii>trali;iii i'r;;ii 



192 THE EFFECTS OF CLIMATE ON ANIMALS 

the Asiatic yak cannot be used in Africa. Many animals, like the 
horse, the sheep, the dog, the cat, the hen, the goat, the cow, and 
the pig, have been able to adapt themselves to climatic conditions all 
around the world as thoroughly as man himself. All, however, need 
the food and the shelter provided by man. 

Life in the Sea. — Marine animals depend directly or indi- 
rectly for food upon the vegetation which flourishes in the sea or the 
food material brought by rivers from the land. Life in the sea is most 
abundant in the shallow waters of the continental shelf. Owing to 
their great area and depth, the oceans support more animal life than 
the land. Among the higher land animals some live in the water, 
though they are not water-breathers. Among the birds, the penguins 
swim under "water in pursuit of fish. The whale, the dolphin, the 
sea cow, the seal, and the walrus are all warm-blooded animals which 
cannot live more than a few minutes under water. 

QUESTIONS. — (1) Name the barriers which divide the earth into the five animal 
regions. (2) In what respects does the animal life of the Arctic belt differ from that 
in the hot belt? (3) How is the camel superior to the horse in the desert? (4) Show 
how the cat, the tiger, the mole, the antelope, and the frog are adapted by nature to their 
environment. (5) What effect is produced by man on the flesh and grass eating ani- 
mals? (6) Which animals of the world could not exist in North America? (7) Why aro 
the animals of Australia so different from other animals of the world? (8) The rabbit, 
introduced by white men into Australia, has multiplied so rapidly as to become a pest. 
Why? (9) What South American animals could exist in Africa? (10) What plant 
and animal life is likely to be found in the newly discovered Antarctica? (11) Name 
five typical animals of the desert regions, the tropical forests, the tundras, the grass- 
lands. (12) What North American animals have been brought from other countries? 
(13) Why cannot animals readily migrate over mountains or across deserts? (14) Name 
the countries in which you can find in its native home the opossum, the camel, the 
cougar, the giraffe, the antelope, the armadillo, the emu, the condor, and the musk ox. 
(15) Show the importance of the following features to each of these animals: the scales 
and tail of a fish; the neck of the giraffe; the trunk of the elephant; the stripes of the 
tiger and zebra; the shell of the clam; the coloring of fish. (16) What other examples 
of this principle do you note in the illustrations of this chapter? 



CHAPTER XVI 



THE EFFECTS OF CLIMATE ON MAN AND HIS ACTIVITIES 



The Influence of Climate on Man. — The highest creature 
over which chmate exerts any control is man. But whether in his 
civiUzed state or in his condition of savagery, Hke all other living 
things he too must have air, food, warmth, and moisture; he too is 
dependent upon Nature. From southern Asia, which has been called 
the cradle of the human race, to all the lands over which he has 
spread, man has been driven to activity to secure the two requisites 
for existence, — food and shelter. In this quest he is under the 
bonds of climatic control. 

True, of all creatures on the 
earth man is the one best able to 
adapt himself; but he cannot exist 
for any length of time in regions 
whore there is no water, nor plant 
or animal life. Climate is a more 
important factor in man's life than 
the various forms assumed by the 
earth's c^-ust in its cooling and chang- 
ing. The influence of climate is 
greater than that of ocean, moun- 
tain, desert, river, volcano, prairie, 
and jungle. Climate determines 
where man shall not live, how he shall 
live in those lands which he does in- 
habit, and largely to what degree of 
civilization he shall advance. 

Man in the Climatic Zones. — As we should expect, regions of 
permanent ice around the poles and on mountains arc uninhabited. 
We have seen that agriculture in the Arctic belt is impossil)lr. The 











1 


m 


yj^tt^^Ai 


P 






t 


'^Mt£:im^iwvmK^m^<*^3rssm 



Vu:. !.',(■,. L.'ipl.iiiiIiTs. 



194 THE EFFECTS OF CLIMATE ON MAN AND HIS ACTIVITIES 

few animals there can support only a sparse population. Here live 
the Eskimos. Being forced to depend on animals alone, they use 
their flesh for food, their skins for clothing and summer tents, and 
their bones for spears and for the framework of their kayaks or boats. 
All the energy of people in these polar regions is directed to securing 




Fig. 157. An Indian camp iu Canada. 

food and shelter, and little opportunity is afforded for their develop- 
ment and better civilization, so that they remain savages dwarfed 
in body and in intelligence {Figure 14-9)- 

In the torrid zone conditions are quite the opposite to those in 
the Arctic. The plant and animal life supply an abundance of food 
ready to the hand of man. He has little need for shelter or clothing. 
Practically no effort is required on his part to obtain and prepare the 
necessities of life. Indeed, the rains, heat, and dampness prevent the 
carrying on of any steady work. As a result, the natives of this zone 
have emerged scarcely above the state of animals. They are in- 
dolent, unintelligent, and without ambition. They comprise the 
negroes of Africa, the natives of Australia and the Philippines, and 
the Indians of Central America and South America. 

In these two zones climate is an inflexible taskmaster. So cold 
and so barren are the Arctic lands, so enervating the torrid climes, 
that the natives have to live from hand to mouth. Division of labor 
is unknown among them. Each family gets or makes what it needs 



THE TEMPERATE ZONES 



195 



for its own members. They hunt and fish or {gather edible roots 
or the fruits of plants about them. The men are the hunters and 
fighters, the women prepare the food and carry the burdens. Their 
homes meet the demands of oHmate; they keep out the icy wind, lift 

the family above the equatorial 




Vit,. l.JN. ,Sa\at£:<'.s ill the interior of the Pliilip- 
pines and their home in course of construction. 



dampness, or shield the 
members from the sun. 
These hunting and fishing 
races need a large area to 
furnish the food necessary 
for only a few people, so 
that their tribal or village groups are small, comprising only a few 
families. They have no fixed abode, but the groups move about the 
country after the game or as they wish. Their weapons and imple- 
ments are of the simplest kind. 

The Temperate Zones. — In these regions we find the happy 
medium between the two extreme effects of climate. Here the winters 
are not too cold nor the summers too warm. In our study of plant 
and animal life we found that nature here gives to man, init not with 
a lavish hand. In this l)elt the most useful plants grow and the do- 
mesticated animals can increase. Man must put forth some effort to 
secure what he needs. He must learn to ho prudent and watchful to 
meet the climatic changes: he must store food in summer to eat in 



196 THE EFFECTS OF CLIMATE ON MAN AND HIS ACTIVITIES 

winter. To provide food and to secure shelter he must spend his 
energies with intelhgence and foresight. In this belt, in the middle 
latitudes of North America, Europe, and eastern Asia, we shall find 
the most progressive and most highly civilized people of the world. 
We must not expect the human race to be evenly distributed over 
the temperate zones. This could happen only if there were no other 
conditions than those of climate. Of course, man will find the great 
coastal plains, where the climate permits outdoor life all the year 
round and where there is abundant moisture, more favorable for his 
home than the tops of inland plateaus. Mature, level valleys, flood 
plains, and broad, fertile deltas will shelter the greatest number of 




Fig. 159. Homes in a Kafir village. 



people. Note, for example, the population at the lower end of the 
Nile {Figure 163). 

Man in Desert Regions. — There is a condition of life in 
which climate forces man to live, that is midway between the savage 
and the civilized states. People in this state, types of whom are the 



KACES OF MANKIND 



197 



Arabs of Asia and Africa, the tribes of Sib(>ria anfl Tartary, the 
Pueblo Indians, and the Aztecs of Mexico, either carry on grazing 
and follow their herds and flocks as the seasons change, or raise scanty 
crops from the barren soil in a primitive way. They are called bar- 
barians. The wandering barbarians or nomads who live largely on 




Fig. IGO. Indian rubber gatherers and their homes along the Amazon river. 



the sandy deserts are made intelligent, hardy, and daring l\y their 
constant struggle for existence. They have domesticated their ani- 
mals and developed simple industries; but there is little division of 
labor or community life, each tribe and famil}' looking after its own 
needs. Then the desert l)arrier prevents these people from learning 
from the people of other and more favored ri^gions. 

Races of Mankind. — Despite the many differences among men 
in race and color, in modes of life and in religion, all are believed to 
have come from a common stock. The influences of different climatic 
conditions, determining the nature of the foods and the modes of life, 
are supposed to have brought about the wide racial variations. On 
account of these differences, we usually tlivide mankind into five 
great class(>s or races. 

The White or Caucasian Race is the high(>st type. Its memliers 
have advanced farllicst in civilization; they are the great discov- 
erers, inventors, and manufacturers. They have migrated most ex- 
tensively, driving out and supplanting weaker races. The Anieri<'an 
Indians were driven from the Atlantic to the West by the European 



198 THE EFFECTS OF CLIMATE ON MAN AND HIS ACTIVITIES 

whites. To-day, whatever development is taking place in the torrid 
zone is being accomplished by members of the white race. The white 
race comprises many nations speaking many tongues; in New York 
City there live thirty-five different nationalities, each speaking a lan- 
guage of its own. The activity and enterprise of the white race have 
placed the white man foremost in North and South America, Europe, 
and along the coast of Australia, and in all the tropical countries. 

Among the peoples of the Caucasian race, there are three well- 
marked types. The Baltic type is blond or florid, with reddish hair, 
blue eyes, and tall stature. It includes Scandinavians, Germans, 




Fig. 161. The homes of cliff dwellers in Arizona. 



Am. Mus. Nat. Hist. 



English, Scotch, and Irish, West Persians, and Hindus. The Alpine 
type, with light brown complexion and hair, brown, gray, or black 
eyes, broad skull, and medium stature, includes the French, Welsh, 
South Germans, Swiss, Russians, Poles, Bohemians, East Persians, 
and Armenians. The Mediterranean type, with olive brown to black 
skin, black hair and eyes, and small stature, includes the Spanish, 
Portuguese, some French, Welsh, and Irish, Italians and Greeks, 
Egyptians, Arabs, Syrians, and some Hindus. 

The Yellow or Mongolian Race inhabits all of Asia not occu- 
pied by the Caucasians. The Chinese branch includes the people of 



FIVE RACES OF MANKIND 



199 




Fig. 162. TIi.' l>v Um.-os of M:inkin.l I 111.- K.-^l J 1 n.- .Mii,\ -I 1.1 
3, The White or Caucutjiuii. 4. The Black, o. I'hc Yellow. 



200 THE EFFECTS OF CLIMATE ON MAN AND HIS ACXIVITIES 

China, Tibet, Siam, and Indo-China. The Siberian branch includes 
the Manchus who conquered China in the seventeenth century, the 
Turks, the Cossacks, the Eskimos, the Finns, the Lapps, the Japanese, 
and the Koreans. Dwarfed stature among the Eskimos, Finns, and 
Lapps has resulted from the severe cold and the long polar night. The 
Mongolians are characterized by their coarse, straight hair, small 
noses, and the oblique appearance of the eyes. They cling tenaciously 
to old customs, but the influence of the white race seems to be arous- 
ing them. The Japanese is the most active and progressive nation 
of this race, and its members are called the Yankees of the East, hav- 
ing by deliberate adoption added to their native civilization the most 
advanced ideas of the Caucasians. 

The Brown or Malay Race consists of the dark-skinned people 
of the Malay Peninsula and the Straits settlements, including the 
Philippines, Java, Sumatra, New Zealand, and New Guinea. The 
members are small in stature and low in order of civilization. 

The Black Race occupies all the tropical regions of the con- 
tinents of Africa and Australia and many of the Pacific island chains. 
It is thought that the dark skin of this race is due to Nature's efforts 
to protect man from the heat and moisture of the tropics. The 
inhabitants of all warm countries tend to become dark-skinned. Take 
the Hindus, for instance, who, except for their dark skin, have no 
other feature in common with the negro race and are classed with the 
white stock. 

The control of climate is seen clearly in the indolent unprogress- 
iveness of the members of the black race. They are a people fitted 
carefully by nature for life in the hot belt. The race includes among 
others an unusual variety of small men about four feet in height, their 
stature due to lack of sunlight, known as the Pygmies, who inhabit 
the forests north of the Kongo. The yellow and the black races have 
seldom migrated from their native homes. The negroes who have 
gone to other lands have mostly been carried as slaves to the western 
hemisphere. They are scattered to-day very widely through Brazil, 
West Indies, Peru, United States, and Mexico. 

The American or Red Race includes all the native inhabitants 
of the western hemisphere. Since the characteristics of this peoplSj 
the reddish-brown skin, small eyes, and straight black hair, are so 



202 THE EFFECTS OF CLIMATE ON MAN AND HIS ACTIVITIES 

similar to those of the yellow race, we believe that the North Amer- 
ican Indian may have been of Asiatic origin. Weapons and relics are 
sometimes found which seem to strengthen this suggestion that tribes 
crossed over Bering strait. This race includes all the various tribes 
once the inhabitants of our country from ocean to ocean, the Pueblos 
and the Cliff-dwellers, the Aztecs and the other tribes of South Amer- 
ica and the West Indies, and the rude Patagonians and Fuegians. 
For centuries they have given way before the white race, and only 
those members are surviving who are adopting the ways of their 
conquerors. 

The Population of the World. — The total number of inhabit- 
ants of the world spread over the earth, as shown in Figure 163, ex- 
ceeds 1,650 millions. The white or Caucasian race makes up 52 per 
cent of this number, the yellow and brown races 36 per cent, the black 
race 11 per cent, and the red race 1 per cent. We can see also that 
the large groups of dense population are all in the northern hemi- 
sphere, and mostly between the tropic of Cancer and the Arctic circle. 
About 80 per cent of the world's people live between the annual iso- 
therms of 40° and 70°. We have already learned why this climate 
favors the denser population. 

In any region the population will always depend upon the 
facilities for obtaining food. We may look for heavy populations 
in warm lowlands without excessive rainfall; for example, in 
southeastern Asia, where one half the people of the world raise 
their own food products. On the other hand, cooler and drier 
lands will support heavy populations if abundant and unfailing 
supplies of food from other countries can readily be brought in by 
sea or by rail. In western Europe, one fifth of the world's people 
subsist largely by buying food from Asia, eastern Europe, and 
America. 

Effects of Climate on Man's Activities. — The climate of a region 
generally determines the industries which may thrive there. Lum- 
bering, and the production of turpentine, tan bark, and rubber can 
thrive only where there is sufficient rainfall to maintain forests. Cli- 
mate determines what kinds of crops shall be raised, whether corn, for 
example, or wheat, rice, sugar cane, coffee, alfalfa, tobacco, or cotton, 
etc. Stock raising is also controlled by climatic conditions. Graz- 



EFFECTS OF CLIMATE ON MAN's ACTIVITIES 



203 



ing and h(>r(lins can l)o conductofl profital)Iy only when* ^rass will 
grow abundantly. Farmers in our North and Sou.th Atlantic states, 
in England, Germany, and India, raise cattle in a small way; hut with 
herds of thousands of cattle, goats, sheep, and horses, the stock-rais- 
ing industry is carried on best in regions too dry for ordinary farming. 
These are the semi-arid plains, steppes, llanos, and pampas of Russia, 




Fiu. 164. How man seeks the shelter of a protected valley for his home. 



South Africa, Argentina, Spain, Australia, Mexico, and the Great 
Plains of our West. 

If man engages in manufacturing, he is checked again by climate, 
because he must have all the raw materials which can be provided 
only by the industries mentioned before. The success of the wheat, 
sugar, cotton, and tobacco crops concern the great milling establish- 
ments, the sugar refineries, the textile mills, and the cigar factories. 
We have seen the effect of weather changes on certain manufactures. 



204 THE EFFECTS OF CLIMATE ON MAN AND HIS ACTIVITIES 



There are other industries, such as salt evaporating and open-air 
fruit drying, which depend upon dry climate conditions. 

Effects of Climate on Commerce. — Among savage peoples, 
ever}" man seeks only the necessaries of life for his own family, without 
help from others. In his civilized state man follows many varied 
industries, and there is a division of labor. This means that each 
worker gives most of his time to one industry, and later exchanges the 
product he cannot use himself for other things that he needs which 

are produced b}^ other 
men. We have seen 
how climate deter- 
mines man's needs 
and what he can 
produce. England 
cannot produce the 
enormous amount of 
wheat and sugar she 
consumes, so she has 
to rely on the wheat 
and sugar producing 
countries for these 
commodities. In this 
way there is a great 
division of labor among nations also, and an interdependence of one 
region upon another. In the same way, the various classes of people 
in a region depend one upon the other, wliile all are dependent upon 
the farmer who takes the world's food from the soil. 

Not only does climate determine what commodities shall be ex- 
ported or imported by nations, but it influences largely the methods 
and the facilities of transport. Climate both permitted and compelled 
Great Britain to become a great commercial nation. For, while she is 
favored with a climate mild enough not to block her ports with winter 
ice, she has to fight against and master the seas from over which her 
ships bring the supplies for food and manufactures. 

The location of railways, bridges, grain elevators, factories, and 
wireless stations is normally controlled by temperature, wind, mois- 
ture, and other climatic elements. Railroad communication is ob- 




FiG. 165. How man in the tropics seeks a home on a 
mountain to avoid the heat of the lowlands. 



OTHER EFFECTS OF CLIMATE ON MAN 



205 



structed by snow in Canada, Scotland, and our western states; in the 
deserts by the effects of wind-driven sand; and in the moister part 
of the tropics the luxuriant vegetation greatly handicai)s the con- 
struction of new lines. 

Other Effects of Climate on Man. — Climate affects the life of 
man in many minor wa^^s. It generally determines what kind of shel- 
ter he must rear to house himself in. The Eskimo finds his igloo warm 
and comfortable in the winter, but the suunucr di-ivcs him to his 
skin tupic. The na- 
tive of the tropical 
forest makes his hut 
of bamboo, palm, 
and cocoanut leaves, 
sugar-cane, and 
grass. In the rainy 
season he is forced 
to erect structures in 
the trees or on piles. 
In the tropical deserts 
the dwellings are of 
stone with flat rocks 
on which the people 
sleep at night. In 
continental countries 
the walls of houses are commonly built thicker than in maritime 
countries, in order to check the entrance of extreme heat and cold. 
In Canada double windows are used. In southern Europe carpets 
are rare, bare stone or wooden floors being used as a protection 
against the summer heat. In the Mediterranean countries the houses 
are generally white in color to reflect the sun's heat. 

In cold climates man needs more heat-producing foods, lik(> fat, 
oil, and sugar, than in warmer climes. The Eskimo lives entirely on 
animal food; while in the tropics the diet of the natives consists of 
vegetable products, such as the banana, cocoanut, breadfruit, rice, 
yams, sago, and, in the desert oases, the date. The nations of the 
temperate zones require a diet of mixed animal ant! vegetable fooil. 

Climate affects the dress and clothing of man antl his modes of 




Fig. 166. A group of native hiits iu Jamaica. 



206 THE EFFECTS OF CLIMATE ON MAN AND HIS ACTIVITIES 

locomotion. The Eskimos traverse the frozen snow in clog or rein- 
deer sledge, while equatorial natives move about the flooded coun- 
try so much in boats that certain tribes scarcely know how to walk. 
Besides temperature, humidity, wind and sunshine, there is another 
element of climate which influences very widely the habits of people 
with respect to indoor and outdoor life, and that is the varying length 
of the day in summer and "u-inter in the different latitudes. In low 
latitudes, between 45° north and south of the equator for example, the 
gTeat contrast between the length of the day in June and December 
that is so remarkable in higher latitudes is missing. The habits of 
people in low latitudes will therefore vary comparatively little with the 
seasons, while people living farther north and south will spend a great 
part of the summer in the open air but will be forced to live indoors 
during the colder periods. iMoreover, climate determines man's sports 
and national games. In Canada, except on the Pacific coast, the 
winter is the gay season of merriment. Skating is enjoj^ed in the 
more eastern countries of Europe, curling in Scotland, and skiing in 
Norway. Switzerland, on account of the longer days, however, is 
the winter plaj'ground of Europe rather than Norway. In Colorado, 
tennis and skating are enjoyed at the same time in the dry and bright 
frosty conditions. 

QUESTIONS. — (1) What zones are most favorable to the phj-sical and mental 
d3velopnient of man and for what reasons? (2) Upon what conditions are all men de- 
pendent? (3) Why do not the Eskimos advance? (4) What conditions in the tropical 
zone are unfavorable to ci'S'ilization? What is the condition of the native inhabitants? 
(5) How does the life of a savaga differ from that of a barbarian? Where maj^ tjT)es of 
these people be met with to-day? (6) Why are so few members of the brown race seen 
in New York? (7) What is an important cause of the differences among men? How 
does ci-^dlized man differ from the other types? (S) Give reasons for the spread and 
success of the Caucasian race. (9) What characteristics are we likely to find among 
mountaineers? (10) How are the members of the black race fitted to their native en- 
^•ironment? (11) In what ways are Indians adopting the customs of the white race? 
(12) Why do men live near rivers? (13) Upon what does the population of any region 
depend? (14) What climatic conditions are favorable to the advance of the United 
States? (15) Why do men gather in great cities? (16) Show how climate affects the 
houses, clothing, and habits of man. (17) How does climate affect the education of a 
native boy on the Amazon, a Kafir boy, a Chinese boy, an Eskimo boy? (IS) On Figure 
163 account for the population of Australia. (19) Whj' are the densely populated areas 
of South America all near the coast? (20) How is Boli\da dependent on Argeiitina? 
Why does Europe depend on Russia? Why is Siberia bound to grow in importance? 
(21) How does England depend on North America? How does New York depend on 
the West? How does the West depend on New York? 



EXERCISES 207 

EXERCISES. — (1) Make a drawing of a favorable and an unfavorable coast 
line. Tell the effect of a ooa.'st line on the dovolopmont of a country. (2) Find instances 
on Figure 163 where mountain, desert, and water barriers restrict population to certain 
regions. Name these barriers. (;i) Write statements showinR how the climate of Cuba, 
Iceland, Siberia, Brazil, Alberta, Mexico, and Argentina affects the life of the inhabitants 
of each. (4) What other causes besides climate affect the occupations of the people 
of a region? Consider New England, Nova Scotia, Gcrmanj', Japan, and England. 
(5) Make a list of the divisions of the human race, and tell where each is found. (6) De- 
scribe the features and characteristics as you have observed them of the yellow, black, and 
red races. (7) Make a list of ten occupations practiced in New York, and tell how the 
workers depend one upon the other. (8) On an outline map of the western hemi- 
sphere darken the most densely populated regions. Account for this population. 
(9) Make a list of all the nationalities of the Caucasian race in New York, and classify 
them under the three types. (10) Show how the indu.strics of the United States are 
determined by the climate. (11) What facts account for the importance of the British 
nation? 



CHAPTER XVII 
HOW MAN CONQUERS HIS ENVIRONMENT 

The plant, the animal, and the savage accept the conditions of 
their surroundings placidly or die off after struggling vainly against 
an unfavorable environment. Civilized man alone, and especially of 
the races living in the north and the south temperate belts, attempts 
to change his environment, to make it more favorable, and to adapt 
it to his needs. For these reasons, man changes the surface of the 
earth, he outwits the tricky changes of the weather, and fights to 
overcome the effects of climate; he is tireless in his conquest of the 
forces of the sea, and he attempts the mastery of the air. 

Man and the Earth's Surface. — The efforts of millions of men 
are continually directed to making the earth a better home. Where 
man needs land that is covered by a swamp, the water is drained off, 
the land filled in, vegetation is introduced, and soon, as in Florida, 
oranges or other useful products grow. One twentieth of the surface 
of Europe has been drained in this way, and it is still possible in the 
United States to drain 78 million acres, which is now swamp land. 
Where sand dunes encroach upon his homes near the shore, he plants 
trees and shrubs to check their advance. He tears out the heart of 
mountains for their minerals, and blows off the face of great cliffs 
and palisades. 

When rivers and lakes interfere with man's development, he 
undertakes to check their natural course. In every continent he has 
dammed streams to make reservoirs to store water for his use. The 
Ashokan dam system can supply 770 million gallons per day to New 
York City. When old rivers, like the Mississippi, overflow their flood 
plains, he builds levees along the banks to confine the waters. To 
build the Panama canal, the Chagres river was turned out of its 
course; in Wyoming, a river was diverted into a valley to make a 
lake. In the Sahara, man tries to overcome the desert by drawing 
up water through artesian wells. 

208 



MAN AND THE EARTH S SURFACE 



209 



Man brinp;s the plants and animals of one region into another to 
help supply his needs. The Angora goat, the camel, and the ostrich 
are thriving in our West. He even imports one animal or plant to 
live upon and thus kill off another harmful species. Often he makes 
no improvement on Nature; for example, we have vast areas in the 




Fig. 1G7. Oil wells in a California oil region. 



United States which have been deforested to furnish lumber. Great, 
bare, arid scars are left in this way. dermany and France, on the 
other hand, are changing the earth's appearance by planting every 
year hundreds of thousands of trees. 

Man drives deep wells into the earth for water, gas, and oil, and 



210 



HOW MAN CONQUERS HIS ENVIRONMENT 




thus brings these substances to the surface for his use. In his search 
for coal, iron, copper, and other mineral products, the strata are 
wrenched and blasted, and honeycombed with shafts and tunnels. In 
quarrying and mining, great gaps are dug in the surface at one place, 

and huge hills of 
waste materials 
built up at others. 

Where a harbor 
is needed, man with 
his giant dredges 
deepens a waterway 
or blows out great 
rocks and shoals. 
When a hill is in 
the way of some 
improvement, it is 
removed ; when land 
in great cities is 
densely populated 
and is therefore very 
valuable, man builds huge structures for himself to work in or live, 
calling them skyscrapers. 

Communication and Transportation. — Savage tribes have little 
communication with one another. Civilized man in the spirit of 
helpfulness, which is his great characteristic, would make the whole 
world one huge family. Nothing has spurred him on so much to 
change the earth's features as this desire to surmount all barriers of 
time and space between groups of men. 

Roads extend like countless ribbons everywhere over the inhabited 
globe, and 700,000 miles of railways cross its surface. Where moun- 
tains interrupt their progress, man overcomes the barriers by wonder- 
ful railway tunnels like the mount Cenis, the Simplon, and the St. 
Gothard tunnels in the Alps, the second over twelve miles long. The 
Himalayas, the Andes, and the Rockies have all been pierced to save 
time and promote communication. Eight transcontinental railroad 
lines cross North America; and there is one connecting Vladivostok 
with St. Petersburg. We are likely to see a pan-American line from 



Fig. 168. Cutting a railroad tunnel through the Alps. 



COMMUNICATION AND TRANSPORTATION 



211 




Fig. 169. Swiss railroad lines surmounting ail the difficulties of the mountainous 
regions. 




l-'Ki. 17(». A tunnil und.-r iIk- Hudson river :it X.vv V..rk. 



212 



HOW MAN CONQUERS HIS ENVIRONMENT 



Canada to Argentina; and a Cape-to-Cairo line in Africa will be in 
operation shortly. The Hudson river tunnels in New York were one 
of the most difficult of engineering feats; but now a tunnel under the 
English channel is contemplated, and another under Bering strait is 
proposed. The Oroya railroad in Peru, the highest in the world, is a 

marvel of engineering 
skill, ascending to a 
height of 15,650 feet. 
The Jungfraujoch sta- 
tion of the Jungfrau 
railroad in Switzerland 
is the highest station 
in Europe, situated 
11,400 feet above the 
sea. In our West the 
tracks of the transcon- 
tinental roads creep up 
steep mountain sides 
in loops, and bridge 
canyons, chasms, and 
torrents. Great sus- 
pension and cantilever 
railway bridges, hke 
the one at Niagara 
Falls and the Tay 
bridge in Scotland, 
11,000 feet long, carry 
man over rivers. 
Transportation in a 
great city shows man's 
mastery of the earth. 
In New York he rides 
in the air, on the level surface, and under earth and river. The 
Hell Gate bridge over the East river in New York will be three 
miles in length and will bear four railroad lines. 

The telephone and the telegraph keep the most isolated parts of 
the earth in touch with the busy centers, and ships at sea are always 




Fig. 171. The Gokteik viaduct in Burma. 



COMMUNICATION AND TRANSPORTATION 



213 



in communication with land tlirough wireless telegraphy. A message 
encircles the earth in twelve minutes. The number of messages trans- 
mitted annually over the 1,750 submarine cables of the world is over 
eight million. 

Giant dredges fight constantly against the shifting currents of 
rivers like the Nile, the Mississippi, and the Missouri, that choke up 
their channels with sand. These machines draw up enormous amounts 
of mud and gravel to be carried away in scows, so as to permit man's 







HHI 




r J 


^3 




J3^ 


.n^^^^^ 




11 


iffiil^MB 









c^^^Hl 


^^^dk^&^HJB 



Fiu. 172. Scenes on the Oroya railroad in the Andes. 

ships to pass unhindered. The mud and gravel are dumped on shore, 
thus increasing the acreage. 

Pipe lines filled with petroleum run like great arteries across the 
Middle and South Atlantic states, Texas, California, Germany, and 
Russia, to supply the 300 million barrels of oil man every year changes 
into light, heat, and power. In many places there are pipe lines to 
convey natural gas to distant points. 

Perhaps in no greater way has man shown his power than by con- 
structing canals to connect the waters of different oceans. Just as the 
discovery of gold in California led to the construction of the Panama 
railroad, completed in 1855, so the constant desire of restless man 
to avoid the waste of time and the expense of the trip around cape 
Horn led him to build the Panama canal. Before the opening, a ship 
steamed 15,000 miles from New York to San P>anci.sco. Through 
the canal the voyage is 5,000 miles. In like manner a shipper saves 
8,000 miles from New York to Yokohama and 5,000 miles to Val- 



214 



HOW MAN CONQUERS HIS ENVIRONMENT 



paraiso; 8,000 miles are saved in steaming from San Francisco to 
Liverpool, and 6,500 miles to Genoa. This supreme work of man 
cost 400 million dollars, and also cost many men their lives; but its 
effects in aiding mankind more completely to conquer the earth will 
be very great. 

There are thousands of smaller canals. In Holland, they are more 
common than roads. In the Manchester canal in England, a cotton 
steamer from New Orleans can pass along its thirty-five miles in three 
hours and unload its cargo at the doors of the cotton mills. Five 
thousand vessels a year pass through the Suez canal. Germany, Can- 
ada, China, and the United States have many canals. The Antwerp 
and Liege canal will be 84 miles in length, and the Danube and Adri- 
atic canal 319 miles long. Note on the map the effects these new 
canals will have on Europe. 

Man and the Ocean. — The conflict between man and the sea is 
never ending. Year by year the ocean becomes less of a hindrance to 
his progress. A ship may be thought of as a tiny bit of land moving 
from one region and floating across the water to attach itself to an- 




FiG. 173. A newspaper chart published to show the daily position of steamers at sea. 



other region. Man strives constantly to make the size of this bit 
larger and to make its trip more speedy. The Atlantic is crossed in 
five days by 1,000-foot steamers displacing 50,000 tons, carrying 3,800 
people, and burning daily 1,200 tons of coal. Every day 1,000 ships 
enter or leave the ports of Great Britain. A bushel of wheat is carried 



MAN AND THE OCEAN 



215 



from North Dakota to Liverpool for fifteen cents; lumber is carried 
at a profit from Oregon to China and Cape Colony. A steamer crosses 
the Pacific to Hongkong in twelve days. Note in Figure 173 the num- 
ber of transatlantic liners carrying the people and products of Europe 
to America or vice versa. 

All governments unite in the endeavor to render safe the passage 
of ships over the seas. Charts of every coast showing lighthouses, 











Fig. 174. One of the great Holland dikes at low tide. 



buoys, reefs, and shoals are issued. Vessels are warned of weather 
changes and the action of currents, and of the position of icebergs and 
derelicts. Figure 173, a chart published by a daily paper, is an example 
of the watchfulness maintained over passenger vessels at sea. The 
actions of tides are carefully measured and charted for the benefit of 
vessels entering and leaving port. 

To satisfy his needs, not only does man strive to surmount the 
ocean barrier, ])ut he constantly wrests more land from the sea. He 
pushes out great piers into its waters to supply sliipping facilities, 
for amusement purposes, or because no suitable landing place is avail- 
able. He builds great breakwaters, as at Rio de Janeiro, Calcutta, 
Hongkong, Liverpool, and Seattle, to makc^ harl)ors safer, or he deefx^ns 
the mouths of channels and estuaries to j)erniit his huge liners to enter 



216 



HOW MAN CONQUERS HIS ENVIRONMENT 



the harbors. Inventors are even trying to harness the force of the 
waves by means of a wave-motor which shall use the ceaseless action 
of the water to supply power for electric dynamos. 

" God made the sea, but the Dutch made the land." In Holland, 
the dikes keep out the sea from 50,000 acres of reclauned land. The 
Dutch engineers are now busy with a project to reclaim from the 




Fig. 175. How the Dutch are planning to wrest a great body of land from the 
North Sea. 



ocean the enormous bottom of the Zuyder Zee, by building great 
dikes and then pumping out the water. This district, larger than 
the state of Texas and sufficient to maintain three million people, will 
add 500,000 acres to their territory. Land has been wrested from the 
sea in many seaports like London, Boston, and New York by filling 
in the shallow waters. 



THE CONQUEST OF CLIMATE 



217 



The Conquest of the Air. — The minds of men are busy with the 
conquest of the atmosphere. Already balloons in Germany carry 
freight and passengers on schedule time. In 1912, in France, 1,600 
new machines were built for navigating the air and 12,000 passengers 
were carried. There is 
no important nation 
that does not include the 
monoplane, biplane, and 
dirigible balloon in its 
military and its naval 
equipment. In the 
Italian-Turkish and 
Greek-Turkish war 
aeroplanes proved of 
valuable service. Ex- 
periments are being 
made for the more 
rapid delivery of ships' 
mails through the use 
of aeroplanes when the 
vessels near port. One 
by one man is learning 
the secrets of air cur- 
rents and wind pres- 
sure above the earth. 
Hitherto attempts to cross the Atlantic by means of air fliers have 
failed, but man's inventive genius and daring will yet find a way 
to do this. 

The Conquest of Climate. — Man cannot change climate, but 
he strives constantly to modify its effects. In cold countries he heats 
his house artificially; in Haidarabad, in India, he appends wind sails 
to the outside of his house to catch the wind and aid in ventilating 
the interior. In Australia, an item of furniture is always a canvas 
bag to cool water by evaporation. Only through his conquest of 
climate has the white man been able to live in the unhealthful tropi- 
cal countries. The first step in building the Panama canal was the 
elimination of yellow fever in the canal zone. 




Fig. 176. An aeroplane passing over the Alps at 
height of 13,000 feet. 



218 



HOW MAN CONQUERS HIS ENVIRONMENT 



We have seen how closely the spread of man and animals depends 
on vegetation. Man has been very successful in overcoming the 
effects of scanty rainfall. In many regions he has done this by hold- 




FiG. 177. A California desert before irrigation. 




Am. Mus. Nat. Hist. 



Fig. 178. A part of the same region under irrigation. 



ing back the water that would otherwise run off the land, so as to 
form large artificial reservoirs, and then feeding it out to the land as 



THE CONQUEST OF CLIMATE 



219 



needed. This watorinp; of tlio Ijind, either with the water thus stored 
up or with water diverted from rivers or punipt'd from deep wells, is 
known as irrigation. In Turkestan, India, Italy, and Mexico it has 
been used from time immemorial. 

The results of this work of man arc seen everywhere from Pata- 
gonia to Alberta, from Spain to Indo-China. Regions that would 

otherwise be deserts 
have Ijecomc fertile 
garden spots through 
irrigation. At As- 
suan, in the middk; 
of Egypt, an enor- 
mous dam has been 
constructed across 
the Nile, causing a 





rise of 65 feet in the 
level. When water is 
badly needed in lower 
Egypt for the valuable 
cotton crop, canals dis- 
tribute it. The Nile is 
also dammed at Cairo, 
Siut, and other places; 
no other river in the 
world is so thoroughly 
under the control of man. In India, where 25 million acres are 
irrigated, the systems insure regular and larger crops and reduce 
the danger of famine. 

In the United States, the government has organized a Reclama- 
tion Service to construct irrigation dams and build reservoirs to over- 
come the effects on agriculture of tiie little rainfall received I)y the 
western highlands. Water is obtained from mountain streams and 



Fi<;. 170. The head of a canal in an irrigatinR system. 
Fig. ISU. An irrigated potato field in Coloratlu. 



220 



HOW MAN CONQUERS HIS ENVIRONMENT 



led into great canal systems which supply widely separated farms 
and orchards. Companies have been organized, and farmers pay 
for the privilege of using the water as we pay for gas. The railroads 
are quite willing to advance money to further the scheme. As a re- 
sult, land has increased often 400 times in value, two and three crops 
a year are raised instead of one, cities are springing up, and a new 
rush of settlers has set in. Washington, Oregon, California, Wyo- 
ming, Colorado, and Arizona are benefiting vastly from this over- 
coming of the effects of their climate by irrigation. Ten milHon acres 
are now irrigated and 75 million more may possibly be reclaimed. 

By means of smudges, and even by using oil stoves burning in 
orchards at night, man staves off the dangers of light frosts to tender 
blossoms. He erects snow-sheds over railroad tracks in the West 

and in Canada at 
dangerous points 
liable to avalanche 
falls. Powerful iron- 
peaked vessels are 
built in England to 
ram through the 
thick ice on Lake 
Baikal in Siberia, 
and in the harbors 
of northern Asiatic 
ports like Vladi- 
vostok, to permit 
freighters to enter 
and leave in the 
winter months. 

Can Man Change 
Climate? — We 
have seen the effects 
of the Labrador current on our Atlantic climate and of the turning of the 
Gulf Stream toward Europe. An engineer proposed to Congress the 
building of an ocean jetty or artificial peninsula stretching 200 miles 
from Gape Race, Newfoundland, eastward across the continental 
shelf. The cold Labrador current from the north forced away from 




Am. Mu3. Nat. Hist. 



Fig. 181. How helpless man is before nature's forces. 
A city destroyed by a volcano. 



MAN AND NATURE 221 

the coast by this, would sink under the Gulf Stream and flow south- 
eastward to cool the West Indies. New iMighind, New Jersey, New 
York, and Maryland would have the warm climate of Spain and Italy 
that is natural to their latitude. Icebergs would melt far north, fogs 
would disappear, and Greenland would become fertile. The British 
Isles and western Europe would have a warmer climate than they 
have now, since the Gulf Stream would give up no heat to the Arctic 
current. The great cost and the uncertainty involved will probably 
prevent the carrying out of this unique idea, but it is an example of 
the daring imagination of man. Fifty years ago a Panama canal 
seemed equally impracticable. 

Man and Nature. — The general effect of man's efforts to 
change his environment is insignificant in comparison with what he 
cannot change or conquer. The results of centuries of his work arc 
mere scratches on the face of the planet. The forces of nature often 
remind him of his helplessness. His largest vessel strikes an iceberg 
and goes down like a rowboat. An earthquake and a fire reduce to 
ruins the work of years. One sixty-hour storm on the Great Lakes 
sank three steamers, drove twelve others ashore, and took sixty lives. 
On the same day six ocean liners reached port several days late, 
delayed bj^ storms; on one, a huge wave had injured six passengers 
and wrenched off a ten-ton anchor. Twenty-two inches of snow fall- 
ing about the same time in Cleveland stalled trains, broke down wires, 
and brought about a loss of two million dollars. Considering the age 
of the earth, however, and the brief period man has been here, he has 
indeed accomplished wonders on the face of the planet in conquer- 
ing the forces of nature. 



INDEX 



Africa, continent of, 29. 

Age of earth, IS. 

Air, 84. 

Air pressm-e, measurement of, 145. 

Alaska, glaciers of, 110. 

Alps, 44, 210. 

Altitude, effect of, 162. 

Alluvial plains, 39. 

American ice sheet, 109. 

American race, 200. 

Andes, 25, 212. 

Anemometer, 145. 

Aneroid barometer, 146. 

Animals, 181; distribution of, 182. 

Antarctica, continent of, 31. 

Anti-trades, 114. 

Appalachian mountains, 28. 

Arctic animals, color of, ISl. 

Arctic climates, 179. 

Arctic, man in the, 194. 

Argentina, plains of, 178. 

Ash, volcanic, 100. 

Atmosphere, 20, 86. 

Attraction of gravitation, 22, 23. 

Austraha, continent of, 31. 

Autumnal equinox, 51. 

Axis of earth, 21, 24, 52. 

B 

Barometer, 145. 

Barriers, to animals, 46, to plants, 172. 

Bars, 137. 

Basins, river, 36. 

Bay of Fundy, tides of, 136. 

Belt of cahns, 116. 



Big trees, 178. 

Bii-ds, North American, 184. 

Black race, 200. 

Bhzzards, 93. 

Bore, tidal, 137. 

Breakers, 131. 

Bro'^VTi race, 200. 

Buttes, 43. 

c 

Cables, 212. 

Cactus, 176. 

Calms, belt of, 116. 

Campos, 175. 

Canyons, 43. 

Caucasian race, 197. 

Centersphere, 19. 

Circle of Illumination, 48. 

CuTUS clouds, 92. 

Chmate, 158, 161; of mountains, 45; 

effects of, 171, 181, 193, 202, 204. 
Clouds, 89, 90, 91. 
Coal, 46. 

Coastal plains, 41. 
Coast Unes, 29, 31. 
Color, of animals, 181. 
Colorado canyon, 43. 
Comets, 14, 15. 
Compass, 67. 
Cones, volcanic, 98. 
Constant winds, 119. 
Continental islands, 25. 
Continental sheK, 25. 
Continental divides, 36. 
Continents, 28, 30, 31. 
Craters, 100. 
Crater lakes, 100. 



222 



INDEX 



223 



Crest, of waves, 131, 132. 
Crevasses, glacial, 108. 
Crust, movement of, 27. 
Cumulus clouds, 92. 
Currents, ocean, effect of, 165. 
Cyclonic storms, 125. 

D 

Date Line International, 69. 

Daylight and darkness, 50, 52. 

Deciduous trees, 177. 

Degrees, 66. 

Deltas, 40. 

Deserts, 43. 

Desert vegetation, 175. 

Detritus, 35. 

Dew, 88. 

Dew point, 88. 

Distribution, of animals, 182; of man, 

193. 
Divides, river, 36. 
Domestic animals, 190. 
Drainage, 35. 
Dro'ttTied valleys, 40. 
Dyewood trees, 174. 

E 
Earth, 10, 16. 

Earth's axis, inclination of, 21, 24, 52. 
Earth's crust, 25; size and shape, 18, 20. 
Earthquakes, 104, 105. 
Ebb tides, 133. 

Eclipse, of sun, 81; of moon, 80. 
Elevation, forces of, 25. 
Equable climate, 165. 
Equator, 21. 
Equatorial drift, 1.39. 
Equinoxes, 50. 

Erosion, 25 ; agencies of, 32, 34. 
Eskimos, 194. 
Estuary, 40. 
Etna, 103. 
Eurasia, continent of, 31. 



Evaporation, 85. 
Evergreen trees, 177. 



Fahrenheit scale, 85. 

Fiords, 40. 

Fixed stars, 8. 

Flood plains, 39. 

Flood tides, 133. 

Floods, 155. 

Fog, 88. 

Fold, rock, 44. 

Food of man, 177, 193. 

Forests, 177. 

Frost, 88. 

Fundy, bay of, 136. 

G 

Galveston, 126. 

Geography, how man changes, 208. 

Geysers, 97. 

Glacial erosion, 108. 

Glacial lakes, 109. 

Glacial period, 109. 

Glaciers, 106, 109. 

Gravitation, attraction of, 22, 23. 

Gravity, 22. 

Grasslands, 174. 

Great Lakes, 109. 

Greenwich observatory, 62. 

Ground moraine, 108. 

Gulf stream, 139. 

Gulfs, cause of, 29. 



Hail, 95. 

Halle}', Edmund, 15. 
Harvest moon, 79. 
Hawaiian islands, 103. 
Heat of the earth, 97. 
Heat belts, 160. 
Heat equator, 161. 
Hell Gate, 136. 



224 



INDEX 



Hemisphere, land, 19; water, 19. 
High barometric pressure, 148. 
High pressure areas, 150. 
Homes, selection of, 195, 196. 
Homes of animals, 182. 
Horse latitudes, 117. 
Hot springs, 97. 
Houses, 205. 
Hudson river, 40. 
Humidity, 86. 
Hunter's moon, 79. 
Hurricanes, 126. 
Hydrosphere, 19. 
Hydrometer, 86, 145. 



Land hemisphere, 19. 

Latitude, 59. 

Lava, 98. 

Levees, 156. 

Life, in deserts, 196. 

Life history, of mountains, 44; of river 

valleys, 36. 
Light belts, 54. 
Llama, 186. 
Llanos, 175. 
Local time, 71. 
Longitude, 62. 
Longitude and time, 67. 
Low barometric pressure, 148. 



Ice, 95. 

Icebergs, 110. 

Ice sheets, continental, 109. 

India, climate of, 169. 

Indian race, 200. 

Interior of earth, 19. 

Interior plains, 41. 

International Date Line, 69. 

International Day, 70. 

Irrigation, 219. 

Islands, continental, 25; oceanic, 25. 

Isobars, 149. 

Isothermal charts, 161, 162, 166, 168. 

Isotherms, 161. 

J 

Japan current, 141. 
Jupiter, 10. 

K 

Kamchatka, peninsula of, 31, 164. 
Kangaroo, 190. 
Krakatoa, 103. 

L 

Labrador Current, 141, 167. 

Lake basins, 38. 

Lakes, 38. 

Land breezes, 119. 

Land, changes in level of, 25. 



M 

Magnetic poles, north, 68. 

Malay race, 200. 

Man, 193; and environment, 208. 

Mankind, races of, 197. 

Mars, 10. 

Marsupials, 190. 

Martinique, 101. 

Matm-e mountains, 45. 

Matm-e valleys, 38. 

Mauna Loa, 104. 

Medial moraine, 108. 

Mediterranean, 138. 

Mercury, 10. 

Meridian, 62. 

Meteors, 14, 16. 

Minutes, 66. 

Mississippi, delta of, 40. 

Mistral, 147. 

Mongolian race, 198. 

Monsoon winds, 119. 

Mount Pelee, 101. 

Moon, 75, 79, 81, 82; surface of, 76. 

Moraines, 108. 

Mountains, 44. 



N 



Neap tides, 135. 
Nebula, 13. 



INDEX 



225 



Neck, volcanic, 100. 
Negro race, 200. 
Neptune, 10. 
Nile delta, 40. 
Nimbus clouds, 92. 
Nitrogen, 84. 
Nomads, 197. 
North America, 2S. 
North magnetic pole, 68. 
Northeast trades, 117. 
Northers, 147. 
Norway, fiords of, 40. 

O 

Oases, 44. 

Ocean currents, 138. 

Oceanic islands, 25. 

Old mountains, 45. 

Old valleys, 39. 

Orbit, 9; earth's orbit, 10. 

Oxygen, 84. 



Pacific ocean, 13, 141. 

PaUsades, 100. 

Pampas, 178. 

Pampero, 147. 

Panama canal, 213. 

Peneplain, 40. 

Peninsulas, 29. 

Phases of moon, 77. 

Plains, 39, 41. 

Planets, 8, 10. 

Plants, 171, 173. 

Plateaus, 42. 

Platypus, duck-billed, 190. 

Polar winds, 118. 

Pole star, 8. 

Poles of earth, 23. 

Poles, magnetic, 68. 

Population of world, 202. 

Prairies, 42. 

Pressure of air, 146. 

Prevailing westerlies, 117. 



Prime meridian, 62. 
Pueblos, 197. 

R 

Races, of mankind, 197. 

Races, tidal, 136. 

Rain, 121. 

Rain belts, 12.3. 

Rainfall, of world, 123; of United States, 

128, 300. 
Red race, 200. 

Regions, animal, 182, 184, 186, 190. 
Revolution, of earth, 48; of moon, 76; 

effects of, 118. 
Rivers, 35; basins of, 36. 
Rocks, 32. 
Rocksphere, 19. 
Rocky Mountains, 44. 
Rotation of earth, 48; of moon, 76. 

S 
Sahara, 124. 

St. Got hard tunnel, 210. 
Sand bars, 137. 
Sand dunes, 208. 
Satellites, 14. 
Saturn, 10. 
Savannas, 174. 

Seasons, explanation of, 52, 53, 54, 58. 
Seconds, 66. 
Sextant, 68. 
Simoom, 147. 
Simplon tunnel, 210. 
Sinking of t he land, 25. 
Sirocco, 147. 
Snow, 93. 
Snow crystals, 93. 
Snow line, 46. 
Solano, 147. 
Solar system, 9, 12. 
Solstices, 51. 
South America, 29. 
Southeiust trades, 117. 
Soutii temperate zone, 55. 



226 



INDEX 



Springs, 97. 

Spring tides, 135. 

Standard time, 70; of the world, 72. 

Stars, 7, 8. 

Steppes, 41. 

Storms, 125; prediction of, 147; chart of, 

151. 
Strata, earth, 32. 
Stratus clouds, 92. 
Stromboh, 103. 
Sub-meridian, 62. 
Sun, heat of, 11; sinrface of, 12. 
Surf, 131. 

T 

Temperate zones, 55. 

Temperature, 84, 85. 

Terminal moraines, 108. 

Thermometer, 84, 146. 

Thunderstorms, 126. 

Tides, 133, 134, 135; effects of, 136. 

Timber hne, 36. 

Time and longitude, 67. 

Time belts, 70, 72. 

Tornadoes, 125. 

Torrid zone, 54. 

Trade winds, 114. 

Transportation, 210. 

Tropical plants, 173. 

Tropical zone, man in, 194. 

Trough of waves, 131. 

Tundra, 41. 

Typhoons, 126. 

U 
Undertow, 131. 
United States, rainfall of, 128; storms of, 

150. 
Uranus, 10. 

V 

Valley glaciers, 107. 
Valleys, filling of, 38. 
Valleys, mature, 38. 
Vapor, 86. 
Vegetation and altitude, 176. 



Venus, 10. 
Verkhoyansk, 86. 
Vernal equinox, 50. 
Vesuvius, 103. 
Volcanic ash, 100. 
Volcanic cones, 98. 
Volcanic craters, 100. 
Volcanic plug, 100. 
Volcanoes, 98. 

W 
Warming of air, 113. 
Waterfalls, 38. 
Water gaps, 38. 
Water hemisphere, 19. 
Waterspouts, 126. 
Water vapor, 86. 
Waves, 131; effects of, 132. 
Weather 145; effects of, 153, 154, 155, 

156, 157. 
Weather bureau, 149, 152. 
Weather maps, 149. 
Weathering, 32. 
West coasts, climate of, 165. 
WesterUes, prevaiUng, 117. 
Western America, coast of, 165. 
West Indies, 25. 
West wind drift, 139. 
Whitecaps, 132. 
White race, 197. 
Winds, 113, 114, 118, 119. 
Wind systems of earth, 116. 
Wind work on deserts, 44. 
Winter solstice, 51. 
Winter weather, 153, 154, 155. 
World isotherms, 167. 



Yellow race, 198. 
Yellowstone Park, 98. 
Young mountains, 44. 
Young river valleys, 36. 



Zones, 54, 55. 



APPENDIX 



DIMENSIONS OF THE EARTH 

Polar diameter of the earth 7,800 

Equatorial diameter of the earth 7,020 

Length of the equator 24,002 

Length of a meridian circle 24,857 

Average length of a degree of latitude 

Length of a degree of longitude at the equator 



(I II 11 


10° nort 


11 It II 


20" " 


11 I! U 


30° " 


11 11 11 


40° " 


It It II 


50° " 


It It tt 


60° " 


It II It 


70° " 


It It 11 


80° " 


tt It tt 


90° " 



60 
69.2 
68 
65 
59 
52.3 
44.4 
34.5 
23.6 
12 




Total Area of Earth's Surface 196,907,000 square miles 

Pacific Ocean 70,000,000 " " 

Atlantic Ocean 34,000,000 " " 

Indian Ocean 28,000,000 " " 

Antarctic Ocean 4,998,000 " " 

Arctic Ocean 4,000,000 " " 



Total Sea . 



The Continents 

Area in Sqtiaro Miles 

North America 9,431,000 

South America 6,856,000 

Europe 3,842,000 

Asia 17,056,000 

Africa 11,512,000 

Australia 3,456,000 

Polar Lands 3,756,000 



Total 55,909,000. 



140,998,000 


tt tt 


Inhabitants 


Nunilior 1 


'cr Sq. Mile 


110,000,000 


11.56 


35,000,000 


5.10 


400,000,000 


I06..54 


900,000,000 


.52. 7() 


170,000,000 


It. 76 


8,000,000 


2.31 


300,000 


0.07 


1,623,300,000 


29.03 



11 



APPENDIX 



FACTS ABOUT THE PLANETS 



Name 


Diameter in 
Miles 


Time op Revolu- 
tion AROUND THE 

Sun 


Distance from the Sun in 
Millions of Miles 


Mercury 

Venus 

Earth 

Mars 

Jupiter 

Saturn 

Uranus 

Neptune 


3,000 
7,700 
8,000 

4,500 
87,000 
73,000 
31,000 
35,000 


88 days 
225 
36554 " 

687 
12 years 
293^ " 
84 

165 


36 
67 
93 

13^ times the earth's distance 
5M " " " 

9Q u u (t it 

30 



TIME DIFFERENCE 



Places 



When it is 12 O'Clock Noon 
according to 



Eastern Central Mountain Pacific 



Standard Time in the United States 



At 



London 



Paris 



It is at 

Amsterdam Holland 

Berlin Germany 

Bombay India 

Constantinople Turkey 

Dublin Ireland 

Hamburg Germany 

Hongkong China 

Honolulu Hawaii 

Liverpool England 

London England 

Manila Philippine Is. 

Paris France 

Rome Italy 

Yokohama Japan 



5.20 P. M. 
5.54 p. M. 
9.51 P.M. 
6.56 p. M. 
4.35 p. M. 
5.40 P. M. 
12.37 A. M. 
6.29 A. M. 
4.48 P. M. 
5.00 p. M. 

1.04 A.M. 

5.09 p. M. 
5.50 P. M. 
2.19 A. M. 



6.20 P. M. 
6.54 p. M. 
10.51 p. M. 
7.56 p. M. 
5.35 P. M. 
6.40 P. M. 
1.37 a.m. 
7.29 A. M. 
5.48 p. M. 
6.00 P. M. 
2.04 A. M. 
6.09 P. M. 
6.50 p. M. 
3.19 A. M. 



7.20 P. M. 
7.54 p. M. 
11.51 P.M. 
8.56 p. M. 
6.35 P. M. 
7.40 P. M. 
2.37 A. M. 
8.29 A. M. 
6.48 P. M. 
7.00 P. M. 
3.04 A. M. 
7.09 P. M. 
7.50 P. M. 
4.19 A. M. 



8.20 P. M. 
8.54 p. M. 

12.51 A.M. 

9.56 p. M. 
7.35 P. M. 
8.40 p. M. 
3.37 A. M. 
9.29 a.m. 
7.48 p. M. 
8.00 p. M. 
4.04 A. M. 
8.09 p. M. 
8.50 p. M. 
5.19 a.m. 



12.20 P. m. 
12.54 'p.m. 

4.51 P. M. 

1.56 p. m. 
11.35 a.m. 
12.40 p. m. 

7.37 p. M. 

1.29 a.m. 
11.48 a.m. 



8.04 p. M. 
12.09 p. M. 
12.50 p. M. 

9.19 p. M. 



12.10 P. M. 
12.45 p. M. 

4.42 p. M. 

1.47 p. M. 
11.26 a.m. 
12.31 p. M. 

7.27 p. M. 

1.19 A. M. 
11.39 A.M. 
11.51 A. M. 

7.54 p. M. 



12.41 P.M. 
9.09 p. M. 



